Chapter I: Part 1

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UNIVERSITY OF KANSAS PUBLICATIONS
MUSEUM OF NATURAL HISTORY

Volume 12, No. 14, Pp. 575-655, 10 figs.

May 18, 1964

The Breeding Birds of Kansas

RICHARD F. JOHNSTON

UNIVERSITY OF KANSAS
LAWRENCE
1964

UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY

Editors: E. Raymond Hall, Chairman, Henry S. Fitch,
Theodore H. Eaton, Jr.

Volume 12, No. 14, Pp. 575-655, 10 figs.
Published May 18, 1964

UNIVERSITY OF KANSAS
Lawrence, Kansas

PRINTED BY
HARRY (BUD) TIMBERLAKE, STATE PRINTER
TOPEKA, KANSAS
1964

[Union Label]

30-1476

The Breeding Birds of Kansas

RICHARD F. JOHNSTON

CONTENTS

PAGE
INTRODUCTION 577

DISTRIBUTION OF BIRDS IN KANSAS 579
Avian habitats in Kansas 581
Species reaching distributional limits in Kansas 584

BREEDING SEASONS 588
Introduction 588
Variation in breeding seasons 589
Zoogeographic categories 593
Significance of phylogeny to breeding schedules 595
Regulation of breeding schedules 598

ACCOUNTS OF SPECIES 601

ACKNOWLEDGMENTS 652

LITERATURE CITED 652

INTRODUCTION

The breeding avifauna of Kansas has received intermittent attention from zoologists for about 75 years. Summary statements, usually concerning all birds of the state, have been published by Goss (1891), Long (1940), Goodrich (1941), Tordoff (1956) and Johnston (1960). All but the first dealt with the breeding birds chiefly in passing, and none was concerned primarily with habitat distributions and temporal characteristics of Kansan birds. The present work treats mainly certain temporal relationships of breeding birds in Kansas, but also geographic distribution, habitat preferences, and zoogeographic relationships to the extent necessary for a useful discussion of temporal breeding phenomena.

Information on breeding of some of the 176 species of birds known to breed in Kansas is relatively good, on a few is almost non-existent, and on most is variously incomplete. It is nevertheless possible to make meaningful statements about many aspects of the breeding biology and distribution of most species of Kansan birds; we can take stock, as it were, of available information and assess the outstanding avenues of profitable future work. In the accounts of species below, the information given is for the species as it occurs in Kansas, unless it is otherwise stated. For the various subsections analyzing biology and distribution, only information taken in Kansas is used, and for this reason the analyses are made on about half the species breeding in the state. An enormous amount of observational effort has been expended by several dozen people in order that suitable data about breeding birds of Kansas be available; all persons who have contributed in any way are listed in the section on acknowledgments, following the accounts of species.

Kansas has been described topographically, climatically, and otherwise ecologically many times in the recent past; the reader is referred to the excellent account by Cockrum (1952), which treats these matters from the viewpoint of a zoologist. For present purposes it will suffice to mention the following characteristics of Kansas as a place lived in by birds.

Topographically, Kansas is an inclined plane having an elevation of about 4100 feet in the northwest and about 700 feet in the southeast. West of approximately 97 deg. W longitude, the topography is gently rolling, low hills or flat plain; to the east the Flint Hills extend in a nearly north to south direction, and to the east of these heavily weathered, grassy hills is a lower-lying but more heavily dissected country, hills of which show no great differences in elevation from surrounding flatland.

The vegetation of eastern Kansas comingles with that of the western edge of the North American deciduous forest; a mosaic of true forest, woodland remnants, and tall-grass prairie occupies this area east of the Flint Hills. From these hills west the prairie grassland today has riparian woodland along water-courses; the prairie is composed of proportionally more and more short-grass elements to the west and tall-grass elements to the east.

Climate has a dominating influence on the vegetational elements sketched above. Mean annual rainfall is 20 inches or less in western sectors and increases to about 40 inches in the extreme eastern border areas. Mean monthly temperatures run from 25 deg.F. or 30 deg.F. in winter to 80 deg.F. or 90 deg.F. in summer. The northwestern edges of Caribbean Gulf warm air masses regularly reach northward only to the vicinity of Doniphan County, in northeastern Kansas, and extend southwestward into west-central Oklahoma; these wet frontal systems are usually dissipated along the line indicated by masses of arctic air, sometimes in spectacular fashion. The regular recurrence of warm gulf air is responsible for the characteristically high relative humidity in summer over eastern Kansas and it has an ameliorating effect on winter climate in this region. Almost immediately to the north in Nebraska and to the west in the high plains, summers are dryer and winters are notably more severe. The breeding distributions of some species of birds fairly closely approximate the distribution of these warm air masses; these examples are noted where appropriate below.

DISTRIBUTION OF BIRDS IN KANSAS

Birds breeding in Kansas are taxonomically, ecologically, and distributionally diverse. Such diversity is to be expected, in view of the mid-continental position of the State. Characteristics of insularity, owing to barriers to dispersal and movement, tend to be lacking in the makeup of the avifauna here. The State is not, of course, uniformly inhabited by all 176 species (Table 1) of breeding birds; most species vary in numbers from one place to another, and some are restricted to a fraction of the State. Variations in numbers and in absolute occurrence are chiefly a reflection of restriction or absence of certain plant formations, which is to say habitats; the analysis to follow is thus organized mainly around an examination of gross habitat-types and the birds found in them in Kansas.

TABLE 1.--THE BREEDING BIRDS OF KANSAS

Woodland Species

_Elanoides forficatus_ N[A] _P. bicolor_ O
_Ictinia misisippiensis_ U _Sitta carolinensis_ O
_Accipiter striatus_ U _Troglodytes aedon_ N
_A. cooperii_ U _Thryomanes bewickii_ N
_Buteo jamaicensis_ O _Thryothorus ludovicianus_ N
_B. lineatus_ N _Mimus polyglottos_ N
_B. platypterus_ N _Dumetella carolinensis_ N
_Aquila chrysaetos_ O _Toxostoma rufum_ N
_Falco sparverius_ U _Turdus migratorius_ O
_Colinus virginianus_ N _Hylocichla mustelina_ N
_Phasianus colchicus_ O _Sialia sialis_ O
_Meleagris gallopavo_ N _Bombycilla cedrorum_ N
_Philohela minor_ U _Lanius ludovicianus_ O
_Zenaidura macroura_ N _Sturnus vulgaris_ O
_Ectopistes migratorius_ N _Vireo atricapillus_ N
_Conuropsis carolinensis_ U _V. griseus_ N
_Coccyzus americanus_ N _V. bellii_ N
_C. erythropthalmus_ N _V. flavifrons_ N
_Otus asio_ U _V. olivaceus_ N
_Bubo virginianus_ O _V. gilvus_ N
_Strix varia_ U _Mniotilta varia_ N
_Asio otus_ U _Protonotaria citrea_ N
_Aegolius acadicus_ U _Parula americana_ N
_Caprimulgus carolinensis_ N _Dendroica aestiva_ N
_C. vociferus_ U _D. discolor_ N
_Phalaenoptilus nuttallii_ N _Seiurus motacilla_ N
_Chaetura pelagica_ U _Oporornis formosus_ N
_Archilochus colubris_ N _Icteria virens_ N
_Colaptes auratus_ N _Wilsonia citrina_ N
_C. cafer_ N _Setophaga ruticilla_ N
_Dryocopus pileatus_ O _Passer domesticus_ O
_Centurus carolinus_ N _Icterus spurius_ N
_Melanerpes erythrocephalus_ N _I. galbula_ N
_Dendrocopos villosus_ O _I. bullockii_ N
_D. pubescens_ O _Quiscalus quiscula_ N
_Tyrannus tyrannus_ S _Molothrus ater_ N
_T. vociferans_ S _Piranga olivacea_ N
_Muscivora forficata_ S _P. rubra_ N
_Myiarchus crinitus_ S _Richmondena cardinalis_ S
_Sayornis phoebe_ S _Pheucticus melanocephala_ S
_Empidonax virescens_ S _P. ludoviciana_ S
_Contopus virens_ S _Guiraca caerulea_ S
_Iridoprocne bicolor_ N _Passerina ciris_ S
_Progne subis_ N _P. cyanea_ S
_Cyanocitta cristata_ N _P. amoena_ S
_Pica pica_ O _Spinus pinus_ O
_Corvus brachyrhynchos_ O _S. tristis_ O
_C. cryptoleucus_ O _Loxia curvirostra_ O
_Parus atricapillus_ O _Pipilo erythrophthalmus_ N
_P. carolinensis_ O _Chondestes grammacus_ N
_Spizella passerina_ N

Limnic Species

_Podilymbus podiceps_ U _Butorides virescens_ U
_Phalacrocorax auritus_ U _Florida caerulea_ U
_Ardea herodias_ U _Casmerodius albus_ U
_Leucophoyx thula_ U _Porzana carolina_ U
_Nycticorax nycticorax_ U _Laterallus jamaicensis_ U
_Nyctanassa violacea_ U _Gallinula chloropus_ U
_Ixobrychus exilis_ U _Fulica americana_ U
_Botaurus lentiginosis_ U _Charadrius alexandrinus_ U
_Plegadis chihi_ U _Actitis macularia_ U
_Branta canadensis_ U _Steganopus tricolor_ U
_Anas platyrhynchos_ U _Sterna albifrons_ U
_A. acuta_ U _Chlidonias niger_ U
_A. discors_ U _Telmatodytes palustris_ N
_A. clypeata_ U _Cistothorus platensis_ N
_Aix sponsa_ U _Geothlypis trichas_ N
_Aythya americana_ U _Xanthocephalus xanthocephalus_ N
_Oxyura jamaicensis_ U _Agelaius phoeniceus_ N
_Rallus elegans_ U _Rallus limicola_ U

Grassland Species Xeric Scrub Species

_Buteo swainsonii_ N _Callipepla squamata_ N
_B. regalis_ U _Geococcyx californianus_ N
_Circus cyaneus_ O _Salpinctes obsoletus_ N
_Tympanuchus cupido_ N
_T. pallidicinctus_ N
_Pedioecetes phasianellus_ N Unanalyzed Species
_Charadrius vociferus_ U
_Eupoda montana_ U _Cathartes aura_ N
_Numenius americanus_ U _Coragyps atratus_ N
_Bartramia longicauda_ U _Falco peregrinus_ U
_Speotyto cunicularia_ U _Columba livia_ O
_Asio flammeus_ U _Tyto alba_ U
_Sayornis saya_ S _Chordeiles minor_ U
_Eremophila alpestris_ O _Megaceryle alcyon_ U
_Dolichonyx oryzivorus_ N _Riparia riparia_ O
_Sturnella magna_ N _Stelgidopteryx ruficollis_ N
_S. neglecta_ N _Hirundo rustica_ O
_Spiza americana_ N _Petrochelidon pyrrhonota_ U
_Calamospiza melanocorys_ N
_Ammodramus savannarum_ N
_Passerherbulus henslowii_ N
_Aimophila cassinii_ N
_Spizella pusilla_ N

[A] The letter following each name refers to presumed zoogeographic
derivation of the species, modified after Mayr (1946).
N = North American evolutionary stock;
S = South American stock;
O = Eurasian stock; U = unanalyzed.

Avian Habitats in Kansas

Four major habitat-types can be seen in looking at the distribution of the breeding avifauna of Kansas. These are woodland, grassland, limnic, and xeric scrub plant formations. A little more than half the breeding birds of Kansas live in woodland habitats, about one-fifth in limnic habitats, about one-eighth in grassland habitats, and less than two per cent in scrub habitats; this leaves some 6.4 per cent of the breeding avifauna unanalyzed (Table 2).

TABLE 2.--ANALYSIS OF THE BREEDING AVIFAUNA OF KANSAS BY
HABITAT-TYPES

========================+===============================
| Percentage of the Avifauna of
+--------+-----------+----------
HABITAT-TYPE | | North | Stated
| Kansas | America | Habitat
------------------------+--------+-----------+----------
Woodland: 101 species | 58 | 16.7 | 44.4
Limnic: 36 species[B] | 21 | 6.0 | 38.5
Grassland: 23 species | 13 | 3.8 | 71.3
Xeric scrub: 3 species | 2 | 0.5 | 10.2
Unanalyzed: 11 species | 6 | 2.0 | 55.0
+--------+-----------+----------
Totals: 174 species | 100 | 29.0 | 43.2
------------------------+--------+-----------+----------

[B] Does not include the Canvasback (_Aythya valisineria_),
the Forster Tern (_Sterna forsteri_), and the Black Tern
(_Chlidonias niger_), all recently added to the breeding
avifauna of Kansas.

_Woodland Habitats_

One hundred one species of Kansan birds are woodland species (tables 1 and 2). The analysis of Udvardy (1958) showed woodland birds to be the largest single avifaunal element in North America, with 38 per cent of North American birds relegated to it. It is likewise the largest element in the Kansan avifauna, representing 58 per cent of Kansan birds. Although woodland makes up a relatively small fraction of the vegetational complexes in Kansas, a large number of habitats exist in what woodland is present. An even larger number of possible woodland habitats is clearly missing, however, because the 101 Kansan species actually represent but 44 per cent of all woodland birds in North America, according to Udvardy's analysis. Broad-leaved, deciduous woodlands in Kansas are of restricted horizontal and vertical stratification. More complex deciduous forest associations and all coniferous forest associations are absent from the State.

Using Mayr's (1946) breakdown of geographical origin of the North American bird fauna, about 53 per cent of the woodland passerine birds in Kansas are of "North American" origin, 22 per cent are of "Eurasian" origin, and 14 per cent are of "South American" origin (Table 3). These figures for Kansas are commensurate with those found for other geographic districts at the same latitude in North America (Mayr, 1946:28). Other characteristics of woodland birds are summarized in tables 4 and 5.

TABLE 3.--ANALYSIS OF ECOLOGIC GROUPS OF BIRDS BY STATUS OF
RESIDENCY AND AREA OF ORIGIN

Column headings:
A: Migrant E: N. Amer.
B: Resident F: S. Amer.
C: Pt. Migr. G: Unanalyzed
D: Old World

==========================+=====+=====+=====+=====+======+=====+=====
| A | B | C | D | E | F | G
--------------------------+-----+-----+-----+-----+------+-----+-----
Woodland species, 101:58% | 60% | 29% | 11% | 22% | 53% | 14% | 11%
Limnic species, 36:21% | 94% | 0 | 6% | 0 | 14% | 0 | 86%
Grassland species, 23:13% | 61% | 26% | 13% | 9% | 56% | 3% | 30%
Xeric Scrub species, 3:2% | 33% | 66% | 0 | 0 | 100% | 0 | 0
Unanalyzed species, 11:6% | 64% | 27% | 9% | 26% | 26% | 0 | 48%
--------------------------+-----+-----+-----+-----+------+-----+-----

_Limnic Habitats_

Of Kansan birds, 36 species (20 per cent) prefer limnic habitats (Table 1). Udvardy found this group to represent 15 per cent of the North American avifauna. Kansas is not notably satisfactory for limnic species, and only 38 per cent of the total North American limnic avifauna is present in the State.

Thirty-one species of limnic birds belong to families that Mayr (1946) considered to be unanalyzable as to their geographic origin; of the five remaining species, all seem to be of North American origin. Other characteristics of limnic birds are summarized in tables 4 and 5.

_Grassland Habitats_

Twenty-three species of our total can be called grassland species (Table 1). The subtotal is less than one-fifth of the Kansan avifauna, but it represents 72 per cent of the grassland birds of North America; grassland habitats abound in Kansas. Only 5.3 per cent of all North American birds are grassland species (Udvardy, 1958).

About 56 per cent of these birds are of North American stocks, nine per cent of Eurasian stocks, and three per cent of South American stocks. The percentage of North American species is the greatest for any habitat group here considered. Other characteristics of grassland birds are summarized in tables 4 and 5.

TABLE 4.--ANALYSIS BY HABITAT-TYPE AND RESIDENCY STATUS OF
HISTORIC AVIAN STOCKS IN KANSAS

Column Headings:
A: Woodland E: Unanal. Hab.
B: Limnic F: Migrant
C: Grassland G: Resident
D: Xeric Scrub H: Partly Migrant

=======================+=====+=====+=====+=====+=====+=====+=====+=====
| A | B | C | D | E | F | G | H
-----------------------+-----+-----+-----+-----+-----+-----+-----+-----
Old World Element | 80% | 0 | 8% | 0 | 12% | 11% | 78% | 11%
27:16% | | | | | | | |
North American Element | 69% | 6% | 17% | 4% | 4% | 72% | 14% | 14%
77:44% | | | | | | | |
South American Element | 93% | 0 | 7% | 0 | 0 | 93% | 7% | 0
15:8% | | | | | | | |
Unanalyzed Origin | 22% | 56% | 13% | 0 | 9% | 79% | 16% | 5%
53:32% | | | | | | | |
-----------------------+-----+-----+-----+-----+-----+-----+-----+-----

_Xeric-Scrub Habitats_

Three species of Kansan birds can be placed in this category (Table 1). This is less than one per cent of the North American avifauna, two per cent of the Kansan avifauna, and ten per cent of the birds of xeric scrub habitats in North America. The three species are considered to be of North American origin.

_Unanalyzed as to Habitat_

Eleven species of Kansan birds could not be assigned to any of the habitat-types mentioned above. The total represents two per cent of the North American avifauna, six per cent of the birds of Kansas, and 55 per cent of the species reckoned by Udvardy (_loc. cit._) to be unanalyzable. Fifty-five per cent is a large fraction, but only to be expected: species are considered unanalyzable if they show a broad, indiscriminate use of more than one habitat-type, and such birds tend to be widely distributed.

TABLE 5.--ANALYSIS BY ECOLOGIC STATUS AND AREA OF ORIGIN OF
MIGRANT AND RESIDENT BIRDS

Column headings:
A: Woodland F: Old World
B: Limnic G: North America
C: Grassland H: South America
D: Xeric Scrub I: Unanalyzed
E: Unanal. Hab.

=================+=====+=====+=====+=====+=====+=====+=====+=====+=====
| A | B | C | D | E | F | G | H | I
-----------------+-----+-----+-----+-----+-----+-----+-----+-----+-----
Migrant species | 52% | 29% | 12% | 1% | 6% | 2% | 49% | 12% | 37%
117:67% | | | | | | | | |
Resident species | 73% | 0 | 15% | 5% | 7% | 51% | 26% | 2% | 21%
40:23% | | | | | | | | |
Partly migrant | 64% | 11% | 17% | 0 | 6% | 17% | 66% | 0 | 17%
17:10% | | | | | | | | |
-----------------+-----+-----+-----+-----+-----+-----+-----+-----+-----

Species Reaching Distributional Limits in Kansas

The distributional limits of a species are useful in indicating certain of its adaptive capacities and implying maintenance of or shifts in characteristics of habitats. Although it is generally an oversimplification to ignore abundance when treating of distribution, the present remarks of necessity do not pertain to abundance.

TABLE 6.--BREEDING BIRDS REACHING DISTRIBUTIONAL LIMITS IN KANSAS

Species reaching northern distributional limits

_Florida caerulea_ _Geococcyx californianus_
_Leucophoyx thula_ _Caprimulgus carolinensis_
_Coragyps atratus_ _Muscivora forficata_
_Elanoides forficatus_ _Parus carolinensis_
_Ictinia misisippiensis_ _Vireo atricapillus_
_Tympanuchus pallidicinctus_ _Passerina ciris_
_Callipepla squamata_ _Aimophila cassinii_

Species reaching southern distributional limits

_Aythya americana_ _Empidonax minimus_
_Parus atricapillus_ _Steganopus tricolor_
_Bombycilla cedrorum_ _Chlidonias niger_
_Dolichonyx oryzivorus_ _Coccyzus erythropthalmus_
_Pedioecetes phasianellus_

Species reaching eastern distributional limits

_Eupoda montana_ _Corvus cryptoleucus_
_Numenius americanus_ _Salpinctes obsoletus_
_Phalaenoptilus nuttallii_ _Icterus bullockii_
_Colaptes cafer_ _Pheucticus melanocephalus_
_Tyrannus verticalis_ _Passerina amoena_
_Sayornis saya_

Species reaching western distributional limits

_Aix sponsa_ _Vireo griseus_
_Buteo platypterus_ _V. flavifrons_
_Philohela minor_ _Mniotilta varia_
_Ectopistes migratorius_ _Protonotaria citrea_
_Conuropsis carolinensis_ _Parula americana_
_Chaetura pelagica_ _Dendroica discolor_
_Archilochus colubris_ _Seiurus motacilla_
_Dryocopus pileatus_ _Oporornis formosus_
_Centurus carolinus_ _Wilsonia citrina_
_Myiarchus crinitus_ _Setophaga ruticilla_
_Empidonax virescens_ _Sturnella magna_
_E. traillii_ _Piranga olivacea_
_Parus bicolor_ _Pheucticus ludovicianus_
_Thryothorus ludovicianus_ _Pipilo erythrophthalmus_
_Cistothorus platensis_ _Passerherbulus henslowii_
_Hylocichla mustelina_

_Western Limits Reached in Kansas_

Thirty-one species (tables 6 and 7) reach the western limits of their distribution somewhere in Kansas. Most of these limits are in eastern Kansas, and coincide with the gradual disappearance of the eastern deciduous forest formation. Twenty-nine species are woodland birds, and few of these seem to find satisfactory conditions in the riparian woods extending out through western Kansas. The Wood Thrush is the one woodland species that has been found nesting in the west (Decatur County; Wolfe, 1961). Descriptively, therefore, the dominant reason for the existence of distributional limits in at least 28 of these birds is the lack of suitable woodland in western Kansas; these 28 are the largest single group reaching distributional limits in the State. Many other eastern woodland birds occur in western Kansas along riparian woodlands, as is mentioned below.

Two species showing western limits in Kansas are characteristic of grassland habitats; the Eastern Meadowlark seems to disappear with absence of moist or bottomland prairie grassland and the Henslow Sparrow may be limited westerly by disappearance of tall-grass prairie.

The Short-billed Marsh Wren, a marginal limnic species, reaches its southwesterly mid-continental breeding limits in northeastern Kansas. The species breeds in Kansas in two or three years of each ten, in summers having unusually high humidity.

_Northern Limits Reached in Kansas_

Fourteen species (tables 6 and 7) reach their northern distributional limits in Kansas. Eight of these are birds of woodland habitats, but of these only the Carolina Chickadee is a species of the eastern deciduous woodlands; the other seven live in less mesic woodland. Three of these species (Chuck-will's-Widow, Scissor-tailed Flycatcher and Painted Bunting) have breeding ranges that suggest the northwesterly occurrences of summer humid warm air masses ("gulf fronts") and this environmental feature perhaps is of major importance for these birds, as it is also for the vegetational substratum in which the birds live.

The Lesser Prairie Chicken and the Cassin Sparrow are the two birds of grasslands that are limited northerly in Kansas. Xeric, sandy grassland is chiefly limited to the southwestern quarter of Kansas, and this limitation is perhaps of major significance to these two species. The Scaled Quail and Roadrunner tend to drop out as the xeric "desert scrub" conditions of the southwest drop out in Kansas.

TABLE 7.--ANALYSIS BY HABITAT-TYPE OF BIRDS REACHING
DISTRIBUTIONAL LIMITS IN KANSAS

========================+===============================================
| Habitat-types
DIRECTIONAL +----------+-----------+--------+-------+-------
LIMIT | | | | Xeric |
| Woodland | Grassland | Limnic | Scrub | Total
------------------------+----------+-----------+--------+-------+-------
Western extent | 28 | 2 | 2 | 0 | 31
Northern extent | 8 | 2 | 2 | 2 | 14
Eastern extent | 6 | 4 | 0 | 2 | 11
Southern extent | 4 | 2 | 3 | 0 | 9
+----------+-----------+--------+-------+-------
Totals | 46 | 10 | 6 | 3 | 65
| | | | |
Per cent of the Species | | | | |
in Stated Habitat | 46 | 43 | 14 | 100 | 37
------------------------+----------+-----------+--------+-------+-------

_Eastern Limits Reached in Kansas_

Eleven species (tables 6 and 7) reach their eastern distributional limits in Kansas. Six of these are woodland birds. Four of these are members of well-known species-pairs: the Red-shafted Flicker, Bullock Oriole, Black-headed Grosbeak, and Lazuli Bunting. Presence to the east of complementary species has much to do with the absence of these species in eastern Kansas. Four of the eleven are birds of grasslands, and they drop out as the short-grass prairie is restricted easterly.

The Rock Wren may be considered characteristic of xeric scrub in Kansas, and it is not found to the east in the absence of such scrub.

_Southern Limits Reached in Kansas_

Eight species (tables 6 and 7) reach their southern distributional limits in Kansas. Half of these birds are of woodland habitats, and of these four, the Black-capped Chickadee and Cedar Waxwing are chiefly of sub-boreal distribution. The Black-capped Chickadee also finds its niche partly pre-empted in southern Kansas by the Carolina Chickadee.

The Bobolink and Sharp-tailed Grouse are grassland species that are seemingly adapted to cooler, dryer grassland than is found in most of Kansas.

The Redhead, Wilson Phalarope, and Black Tern are limnic species, perhaps limited southerly by high summer temperatures; the three species are entirely marginal anywhere in Kansas.

TABLE 8.--BIRDS OF THE EASTERN DECIDUOUS FOREST FOUND IN
WESTERN KANSAS IN RIPARIAN WOODLAND

_Accipiter cooperii_[C]
_Coccyzus americanus_[C]
_Centurus carolinus_
_Melanerpes erythrocephalus_
_Tyrannus tyrannus_
_Myiarchus crinitus_
_Contopus virens_
_Sayornis phoebe_
_Cyanocitta cristata_
_Dumetella carolinensis_
_Toxostoma rufum_
_Sialia sialis_
_Vireo olivaceus_
_Icterus spurius_[C]
_Icterus galbula_
_Quiscula quiscalus_
_Piranga rubra_[A]
_Passerina cyanea_
_Richmondena cardinalis_
_Pipilo erythrophthalmus_[C]
_Spizella passerina_[C]

[C] Breeds farther west in North America in other types of
vegetation.

_Influence of Riparian Woodland_

Although the largest single element of the Kansan avifauna that reaches distributional limits in Kansas is made up of birds of the eastern deciduous forest, several species of the eastern woodlands are present in Kansas along the east-west river drainages in riparian woodland; the species are listed in Table 8. Twenty-one kinds are involved if we include the Cooper Hawk, Yellow-billed Cuckoo, Orchard Oriole, Summer Tanager, Rufous-sided Towhee, and Chipping Sparrow, all of which breed farther to the west but are present in western Kansas only along river drainages. This leaves 15 species of eastern deciduous woodlands that occur west in Kansas along riparian woodland (_versus_ 30 species that drop out chiefly where eastern woodland drops out). These 15 species are about one-third of all woodland birds in western Kansas. Riparian woodland does not seem to afford first-rate habitat for most of the eastern woodland species that do occur; breeding density seems to be much lower than in well-situated eastern woodland.

The importance of these linear woodlands as avenues for gene-flow between eastern and western populations, especially of species-pairs (grosbeaks, flickers, orioles, and buntings), is obviously great. Likewise significant is the existence of these alleys for dispersal from the west of certain species (for instance, the Black-billed Magpie and the Scrub Jay) into new but potentially suitable areas.

BREEDING SEASONS

Introduction

An examination of breeding seasons or schedules is properly undertaken at several levels. The fundamental description of variation in breeding schedules must itself be detailed in several ways and beyond this there are causal factors needing examination. The material below is a summary of the information on breeding schedules of birds in Kansas, treated descriptively and analytically in ways now thought to be of use.

Almost any event in actual reproductive activity has been used in the following report; nestbuilding, egg-laying, incubation, brooding of young, feeding of young out of the nest are considered to be of equal status. To any such event days are added or subtracted from the date of observation so as to yield the date when the clutch under consideration was completed.

Such corrected dates can be used in making histograms that show the time of primary breeding activity, or the "egg-season." All such schedules are generalizations; data are used for a species from any year of observation, whether 50 years ago or less than one year ago. One advantage of such procedure is that averages and modes are thus more nearly representative of the basic temporal adaptations of the species involved, as is explained below.

When information on the schedule of a species from one year is lumped with information from another year or other years, two (and ordinarily more than two) frequency distributions are used to make one frequency distribution. The great advantage here is that the frequency distribution composed of two or more frequency distributions is more stable than any one of its components. Second, the peak of the season, the mode of egg-laying, is represented more broadly than it would have been for any one year alone. Third, the extremes of breeding activity are fairly shown as of minute frequency and thus of limited importance, which would not be true if just one year were graphed. All these considerations combine to support the idea that general schedules in fact represent the basic temporal adaptations of a species much better than schedules for one year only.

Variation in Breeding Seasons

In the chronology of breeding seasons of birds, there are three basic variables: time at which seasons begin, time at which seasons end, and time in which the major breeding effort occurs. These variables have been examined in one population through time (Lack, 1947; Snow, 1955; Johnston, 1956), in several populations of many species over wide geographic ranges (Baker, 1938; Moreau, 1950; Davis, 1953), and in several populations of one species (Lack, _loc. cit._; Paynter, 1954; Johnston, 1954). The analysis below is concerned with breeding of many kinds of birds of an arbitrarily defined area and with the influence of certain ecologic and zoogeographic factors on the breeding seasons for those several species.

THE INFLUENCE OF SEASONAL STATUS.--Here we are interested in whether a species is broadly resident or migrant in Kansas; 70 species are available for analysis.

_Resident Species_

Twenty-four species, furnishing 875 records of breeding, are here considered to be resident birds in northeastern Kansas. These species are Cooper Hawk, Red-tailed Hawk, Prairie Chicken, Bobwhite, Rock Dove, Great Horned Owl, Red-bellied Woodpecker, Hairy Woodpecker, Downy Woodpecker, Horned Lark, Blue Jay, Common Crow, Black-billed Magpie, Black-capped Chickadee, Tufted Titmouse, Carolina Wren, Bewick Wren, Mockingbird, Eastern Bluebird, Loggerhead Shrike, Starling, House Sparrow, Eastern Meadowlark, and Cardinal. The distribution of completed clutches (Fig. 1) runs from mid-January to mid-September, with a modal period in the first third of May. Conspicuous breeding activity occurs from mid-April to the first third of June.

_Migrant Species_

Forty-six species, furnishing 2,522 records of breeding, are considered to be migrant in northeastern Kansas. These species are Great Blue Heron, Green Heron, Swainson Hawk, American Coot, Killdeer, Upland Plover, American Avocet, Least Tern, Yellow-billed Cuckoo, Black-billed Cuckoo, Burrowing Owl, Common Nighthawk, Chimney Swift, Red-headed Woodpecker, Eastern Kingbird, Western Kingbird, Scissor-tailed Flycatcher, Great Crested Flycatcher, Eastern Phoebe, Eastern Wood Pewee, Bank Swallow, Rough-winged Swallow, Barn Swallow, Purple Martin, Brown Thrasher, Catbird, House Wren, Robin, Wood Thrush, Blue-gray Gnatcatcher, Bell Vireo, Warbling Vireo, Prothonotary Warbler, Yellow Warbler, Chat, Western Meadowlark, Red-winged Blackbird, Orchard Oriole, Baltimore Oriole, Common Grackle, Black-headed Grosbeak, Indigo Bunting, Dickcissel, Lark Sparrow, and Field Sparrow. The distribution of completed clutches runs from mid-March to the first third of September, with a modal period of egg-laying in the first third of June (Fig. 1). Conspicuous breeding activity occurs from the first third of May to the last third of June.

THE INFLUENCE OF DOMINANT FORAGING ADAPTATION.--Five categories here considered reflect broad foraging adaptation: woodland species, taking invertebrate foods in the breeding season from woody vegetation or the soil within wooded habitats; grassland species, taking invertebrate foods in the breeding season from within grassland situations; limnic species, foraging within marshy or aquatic habitats; aerial species, foraging on aerial arthropods; raptors, feeding on vertebrates or large insects.

_Raptors_

Six species, furnishing 174 records of breeding, are here considered, as follows: Cooper Hawk, Red-tailed Hawk, Swainson Hawk, Great Horned Owl, Burrowing Owl, and Loggerhead Shrike. The distribution of clutches (Fig. 1) runs from mid-January to the first third of July and is bimodal. One period of egg-laying occurs in mid-February and a second in the last third of April. Such a distribution indicates that two basically independent groups of birds are being considered. The first peak of laying reflects activities of the large raptors, and the second peak is that of the insectivorous Burrowing Owl and Loggerhead Shrike. The peak for these two birds is most nearly coincident with that for grassland species, a category to which the Burrowing Owl might well be relegated.

_Limnic Species_

Six species, the Great Blue Heron, Green Heron, American Coot, American Avocet, Least Tern and Red-winged Blackbird, furnish 264 records of breeding. The distribution of clutches (Fig. 1) runs from mid-March to the last third of July and is bimodal. This is another heterogeneous assemblage of birds; the Great Blue Heron is responsible for the first peak, in the first third of April. The other five species, however, show fair consistency and their peak of egg-laying almost coincides with peaks for aerial foragers, woodland species, and migrants, considered elsewhere in this section.

_Grassland Species_

Ten species, Greater Prairie Chicken, Bobwhite, Killdeer, Upland Plover, Horned Lark, Starling, Eastern Meadowlark, Western Meadowlark, Common Grackle, and Dickcissel, furnish 404 records of breeding activity. The distribution of clutches (Fig. 1) runs from the first of March to mid-September. The peak of egg-laying occurs in the first third of May. This is coincident with the peak for resident species, perhaps a reflection of the fact that half the species in the present category are residents in northeastern Kansas.

_Woodland Species_

In this category are included species characteristic of woodland edge. Thirty-four species, furnishing 1,882 records of breeding, are here treated: Yellow-billed Cuckoo, Black-billed Cuckoo, "flicker" (includes birds thought to be relatively pure red-shafted, pure yellow-shafted, as well as clear hybrids), Red-bellied Woodpecker, Red-headed Woodpecker, Hairy Woodpecker, Downy Woodpecker, Blue Jay, Black-billed Magpie, Common Crow, Black-capped Chickadee, Tufted Titmouse, Carolina Wren, Bewick Wren, House Wren, Brown Thrasher, Catbird, Mockingbird, Robin, Wood Thrush, Eastern Bluebird, Blue-gray Gnatcatcher, Bell Vireo, Warbling Vireo, Prothonotary Warbler, Yellow Warbler, Chat, Orchard Oriole, Baltimore Oriole, Cardinal, Black-headed Grosbeak, Indigo Bunting, Lark Sparrow, and Field Sparrow. The distribution of clutches runs from the first third of March to mid-September (Fig. 1). The modal period for completed clutches is the first third of June. Conspicuous breeding activity occurs from the first third of May to mid-June. The distribution of the season in time is almost identical with that for migrant species, reflecting the large number of migrant species in woodland habitats in Kansas.

_Aerial Foragers_

Twelve species, Common Nighthawk, Chimney Swift, Eastern Kingbird, Western Kingbird, Scissor-tailed Flycatcher, Great Crested Flycatcher, Eastern Phoebe, Eastern Wood Pewee, Bank Swallow, Rough-winged Swallow, Barn Swallow, and Purple Martin, furnish 587 records of breeding. The distribution of clutches (Fig. 1) extends from the last third of March to the first third of August, and the modal date of clutches is in the first third of June. Conspicuous breeding activity occurs from the end of May to the end of June. The peak of nesting essentially coincides with that characteristic of migrants.

Zoogeographic Categories

Three categories of Mayr (1946) are of use in analyzing trends in breeding schedules of birds in Kansas. These categories of presumed ultimate evolutionary origin are the "Old World Element," the "North American Element," and the "South American Element." Not always have I agreed with Mayr's assignments of species to these categories, and such differences are noted. There is some obvious overlap between these categories and those discussed previously.

_Old World Element_

Eighteen species, Red-tailed Hawk, Rock Dove, Great Horned Owl, Hairy Woodpecker, Downy Woodpecker, Black-billed Magpie, Common Crow, Black-capped Chickadee, Tufted Titmouse, Robin, Loggerhead Shrike, Starling, House Sparrow, Bank Swallow, Barn Swallow, and Blue-gray Gnatcatcher, furnish 969 records of breeding (Fig. 1). Species for which I have records but which are not here listed are the Blue Jay and the Wood Thrush, both of which I consider to be better placed with the North American Element. The distribution of completed clutches runs from mid-January to the first third of August, and shows a tendency toward bimodality. The second, smaller peak is due to the inclusion of relatively large samples of three migrant species (Robin, Bank Swallow, and Barn Swallow). The timing of the breeding seasons of these three species is in every respect like that of most other migrants; if they are removed from the present sample the bimodality disappears, indicating an increase in homogeneity of the unit.

_North American Element_

Twenty-six species, Greater Prairie Chicken, Bobwhite, "flicker," Rough-winged Swallow, Purple Martin, Blue Jay, Carolina Wren, Bewick Wren, House Wren, Mockingbird, Catbird, Brown Thrasher, Wood Thrush, Bell Vireo, Warbling Vireo, Prothonotary Warbler, Yellow Warbler, Chat, Eastern Meadowlark, Western Meadowlark, Red-winged Blackbird, Orchard Oriole, Baltimore Oriole, Common Grackle, Lark Sparrow, and Field Sparrow, furnish 1,233 records of breeding (Fig. 1). The distribution of completed clutches runs from the first third of April to the first third of September. The modal date for completion of clutches is June 1.

_South American Element_

Twelve species, Eastern Kingbird, Western Kingbird, Scissor-tailed Flycatcher, Great Crested Flycatcher, Yellow-bellied Flycatcher, Traill Flycatcher, Eastern Wood Pewee, Eastern Phoebe, Cardinal, Black-headed Grosbeak, Rose-breasted Grosbeak, and Indigo Bunting, furnish 552 records of breeding (Fig. 1). The curve representing this summary schedule is bimodal, wholly as a result of including the Eastern Phoebe and the Cardinal with this sample.

_Relationship of Schedules to Temperature and Precipitation_

In outlining the ten categories above, attention has been given to certain similarities and differences in the frequency distributions. A slightly more refined way of comparing the frequency distributions is to relate them to other, seasonally variable phenomena. Figure 1 shows the frequency distributions of egg-laying of these ten categories of birds in terms of the regular changes in mean temperature and mean precipitation characteristic of the environments in which these birds live in the breeding season.

Table 9 shows that there are two basic groups of birds according to peak of egg-laying and incidence of precipitation; raptors, birds of Eurasian origin, resident birds, and birds of grassland habitats tend to have their peaks of egg-laying prior to the peak of spring-summer rains, and the other six categories tend to have their peaks of egg-laying occur in the time of spring-summer rains. Regarding temperature, there are four categories of birds; these are evident in the table.

Some of the correspondences deserve comment. Residents and grassland species both breed before the rains come and before mean temperatures reach 70 deg.F., and this correspondence probably results from most of the grassland species being residents. Contrariwise, most birds of Eurasian stocks are residents, but not all residents are of such stocks; the two groups are discrete when mean temperature at breeding is considered. Woodland birds, aerial foragers, and birds of South American evolutionary stocks breed after temperatures surpass 70 deg.F. on the average. Almost all such species are migrants, but many migrants have different temporal characteristics, and the categories thus are shown to be discrete on the basis of temperature at time of breeding.

The change through spring and summer of temperature and precipitation delineates the inception and waxing of the growing season of vegetation and of the subsequent arthropod populations, on which most of the birds feed in the breeding season. The temporal characteristics of growing seasons in North America have been treated by Hopkins (1938) and have been related to timing of breeding seasons in Song Sparrows (_Passerella melodia_) of the Pacific coast of North America (Johnston, 1954).

Significance of Phylogeny to Breeding Schedules

Evidence from a variety of sources demonstrates that timing of breeding seasons is either broadly or specifically genetically-determined. For some species in some situations major environmental variables are paramount in regulating timing of breeding, but in others the innate, regulatory "clock" is less closely tied to conspicuous exogenous stimuli. The work by Miller (1955a, 1955b, 1960) with several species of _Zonotrichia_ strongly indicates that endogenous timing is most important for these birds, and there is ecological evidence for Song Sparrows that supports the same point (Johnston, 1954, 1956). It is, in any event, possible to treat breeding schedules as species-specific characters, for any one geographic area.

In an attempt to relate a breeding schedule to previous ancestral modes, that is by extension to phylogeny, it is necessary to know how often ancestral adaptations can persist in the face of necessity to adapt to present environmental conditions. It is necessary to know how conservative or how immediately plastic breeding schedules can be. The disadvantage of using available information about configurations of breeding seasons (as shown in Figs. 3 to 9) is that it is extremely difficult to compare visually at one time more than six or eight histograms as to the trenchant similarities and differences regarding times of inception and cessation of breeding, and time of peak egg-laying. It is possible, however, to reduce these three variables to one variable (as described below), which allows the necessary comparisons to be made more easily; this variable may be called the _breeding index_.

_Calculation of Breeding Index_

The chronological year is broken roughly into ten-day intervals numbered 1 to 36. The histogram describing the temporal occurrence of the breeding season of a species in our area usually will lie within intervals 7 to 25. The modal date for completion of clutches is given a value corresponding to the number of ten-day intervals beyond interval 7 (March 1-10); this describes the modal variable. The date of completion of 83 per cent of all clutches is given a value corresponding to the number of ten-day intervals it lies from interval 11 (April 11-20); this describes the 83 per cent variable (and is a measure of the length of the season in terms of its inception). The breeding index can then be calculated as follows:

I = X_{m} + X_{sd},

where: I is the breeding index,
X_{m} is the modal variable, and
X_{sd} is the 83 per cent variable.

This is obviously an arbitrary scheme to gain a simple measure of beginning, peak, and end of a breeding season. Other schemes could be devised whereby different absolute values would be involved, but the relative nature of the results would be preserved. The values under the present system for 73 species of Kansan birds run from -5 to +22; early modal dates and cessation to breeding give low values, late dates high values.

Within this framework there are other, presumably subordinate, factors that influence the values of breeding indices, as follows:

1. Migratory habit. Any migrant tends to arrive on breeding grounds relatively late, hence migrants ordinarily have higher index values than do residents.

2. Colonial breeding. The strong synchrony of colonially-breeding species tends to move the modal egg-date toward the time of inception of breeding; as a result colonially-breeding species probably have lower index values than they would have if not colonial.

3. Single-broodedness. Species having only one brood per season tend to have shorter seasons than double-brooded species, and their index values tend to be lower than those of double-brooded species.

Migratory habit unquestionably has considerable influence on index values in some species. It is not, however, as important as other matters, such as the condition of the food substratum or sensitivity of the pituitary-gonadal mechanism, in determining timing and mode of breeding activity. The schedule of the Purple Martin is the extreme example showing that time of spring arrival on breeding grounds is not necessarily related to time of inception of breeding. It should be emphasized that the factors leading to northward migratory movement may be involved in timing of the annual gonadal and reproductive cycle.

Figure 2 presents a graphic summary of values of breeding indices for many groups of Kansan birds. The values for species of a given family have been linked by a horizontal line. The length of this line is proportional to the degree to which the index values for the species concerned resemble one another. Note that the plottings for the Picidae, Corvidae, Turdidae, Tyrannidae, and Icteridae each contain one point that is well-removed from a cluster of points. This can be interpreted as a measure of the frequency of adaptive plasticity versus adaptive conservatism; five of the 24 plottings show a plastic character, 19 a conservative. There are 26 plottings that show temporal consistency, all of which may be taken as evidence of adaptive (or relictual) conservatism of the species in question.

_Conclusion_

Such patterns of breeding chronology support the idea that seasonal response to the necessities of breeding is conservative more often than plastic. Most students of breeding schedules believe that since these are highly adaptive, they must also be capable of flexibility to meet variable environments within the range of the species. Such thinking receives support when different geographic localities are considered for one species (Johnston, 1954), or when specific features of a special environment are considered (see Miller, 1960; Johnston, 1956).

Yet, if one, relatively restricted locality is considered, as in the present study, evidence of a conservative characteristic in breeding schedules can be detected. This conservatism may result from the historic genetic "burden" of the species; that is to say, previous adaptive peaks may in part be evident in the matrix of contemporary adaptation. Adaptive relicts of morphological nature have been many times documented, but characteristics associated with seasonality and timing schedules have not.

In any event, genetic relationships are evident in the configuration of breeding seasons of many species here treated. Thus, any consideration of variation in breeding schedules must be sensitive to the limits, whether broad or restricting, that the heritage of a species sets on its present chronological adaptation.

Regulation of Breeding Schedules

Regulation of breeding schedules in birds always involves some exogenous, environmental timing or triggering mechanism. Broad limits to functional reproductive activity seem to be set by the photoperiod--neuroendocrine system. This basic, predominately extra-equatorial, regulator can be ignored by temperate-zone species only if they possess chronological adaptation to special, aperiodic environmental conditions, as does the Red Crossbill (_Loxia curvirostra_; see McCabe and McCabe, 1933; H. B. Tordoff, ms.), for which the chief consideration seems to be availability of conifer seeds. Environmental phonomena otherwise known to trigger breeding activity include rainfall (Davis, 1953; Williamson, 1956), presence of suitable nesting material (Marshall and Disney, 1957; Lehrman, 1958), temperature (Nice, 1937), and presence of a mate (Lehrman, Brody, and Wortis, 1961). Such regulators, or environmental oscillators, are the "phasing factors" of the physiologic clock that dictate the temporal occurrence of primary reproductive activity.

TABLE 9.--RELATIONSHIP BETWEEN ENVIRONMENTAL FACTORS AND TIMING
OF BREEDING IN BIRDS OF KANSAS

==================+===================================================
| Occurrence of Peak of Egg-laying
+-------------------+-------------------------------
| When | When Mean
| Precipitation is: | Temperature (F.) is:
+---------+---------+-------+-------+-------+-------
| Light | Heavy | < 55 deg. | < 70 deg. | +- 70 deg. | > 70 deg.
------------------+---------+---------+-------+-------+-------+-------
Raptors | x | | x | | |
O. W. Element | x | | x | | |
Residents | x | | | x | |
Grassland species | x | | | x | |
Marshland species | | x | | | x |
N. Amer. Element | | x | | | x |
Migrants | | x | | | x |
Woodland species | | x | | | | x
Aerial foragers | | x | | | | x
S. Amer. Element | | x | | | | x
------------------+---------+---------+-------+-------+-------+-------

None of the regulators mentioned above has been specifically investigated for any Kansan bird, but it is reasonable to suppose that, in these temperate-zone species, the photoperiod is the most important general phasing factor in seasonal breeding. Although gonadal response and seasonal restriction of breeding are set by the photoperiod, specific temporal relationships are dictated by more immediate environmental variables.

Table 9, as already noted, shows the gross relationships between certain groups of birds, certain arbitrary indicators of seasonal temperature-humidity conditions bearing significantly on the growing season, and occurrence in time of peak of egg-laying by the birds involved. Some species and groups of Kansan birds breed chiefly under cool-dry environmental conditions, and some under warm-wet environmental conditions. Within each of these categories some variation occurs. Thus, raptors and boreally-adapted species (the Eurasian zoogeographic element) breed under cool conditions prior to rains, and residents and grassland species breed under slightly warmer conditions prior to rains; limnic species, species derived from North American evolutionary stocks, and migrants tend to breed in the cooler segment of the warm-wet period, and woodland birds, aerial foragers, and species derived from South American evolutionary stocks tend to breed in the warmer segment of the warm-wet period.

So much, then, for relationships between birds and their environments at a descriptive level. It would be useful at this point to examine how environmental variables relate to timing of breeding. Certain independent lines of investigation indicate that birds have a well-developed internal timing device; most convincing is the work of Schmidt-Koenig (1960) and the others who have shown that the endogenous clock of birds can be shifted in its periodicity forward or backward in time. This and much other evidence (see Brown, 1960) indicate that many fundamental periodic regulators are extrinsic to the animal; it is thus permissible for present purposes to consider any expression of variation in timing as dependent on environmental oscillators. It is not hereby meant to ignore the fact that differential responses to dominant environmental variables occur within a species, indicating endogenous control over timing of breeding. The work by Miller (1960:518) with three populations of the White-crowned Sparrow, revealing innately different responses to vernal photoperiodic increase, is especially important in this regard. For the moment, however, we may consider exogenous controls only.

Any exogenous control, or environmental variable, can be looked on simply as a timing oscillator. Such variables show regular or irregular periodic activity, and the independent actions as a whole result in the more-or-less variable annual schedule of breeding for any species at any one place. It would seem that some oscillators are linked to one another, but there is a real question concerning the over-all degree to which linkage is present. It is significant that frequency distributions of breeding activity of various species and groups of birds take on the shape of a skewed normal curve. The more information is added to such distributions, the more nearly they approach being wholly normal, with irregularities tending to disappear. This kind of response itself is evidence that most of the variables influencing the distribution are not mutually linked.

This conclusion is warranted if we examine what would happen to frequency distributions if the variables or oscillators regulating timing were linked. The frequency distribution of breeding activity in birds is described by a nonlinear curve (a normal distribution is nonlinear). Let us assume that each of the environmental variables is a nonlinear oscillator, as is probable. A set of nonlinear oscillators mutually entrained or coupled and operating with reference to a given phenomenon would result in that phenomenon being described by a frequency distribution much more stable than if it were regulated by any one oscillator alone. However, the frequency distribution of a set of coupled nonlinear oscillators is non-normal (Wiener, 1958).

We do not obtain such distributions in describing breeding activity, so we may say that the oscillators regulating such activity are not coupled. Present distribution, habitat preference, residency status, foraging adaptation, previous zoogeographic history, and relicts of ancestral adaptation, all bear on the character of the breeding schedule of any bird species. The emphasis above on multiple regulation of breeding schedules conceivably reflects the true picture, but any such emphasis is made at the expense of taking one factor as basic, or reducing the many to one, in order to manufacture simplicity.

ACCOUNTS OF SPECIES

In each account below information is given concerning status, habitat, geographic distribution, seasonal occurrence, schedule of egg-laying, number of eggs laid, and sites of nests, as these pertain to Kansas, unless otherwise stated. The ways in which some of these points were elucidated are as follows.

1.--Breeding schedule. Frequency distributions of egg-laying in time are calculated on the basis of dates of completed clutches, as described earlier (p. 588). Any event in the series of actions of nesting--nestbuilding, egg-laying, incubation, brooding, feeding young out of nests--can be manipulated by adding or subtracting days to or from the date of record to yield the probable date of completion of the clutch. The resulting data are grouped into class intervals of ten days. Extreme dates here given for egg-laying may be as much as nine days off in accuracy, but the error does not often exceed five days. Extreme dates indicated here may be taken as actual or predicted extremes. The raw data used are on file at the Museum of Natural History and are available for use by any qualified individual.

2.--Dates of occurrence. First and last annual occurrences in the State for migrant species are indicated by both a range of dates and a median date. Twenty to 30 dates of first observation in spring are available for most of the common species, and 10 to 20 dates of last observation in autumn are at hand for such species. The median dates, earlier than and subsequent to which an equal number of observations are available, are reliable indicators of the dates on which a species is likely to be seen first in the State in an average year.

3.--Clutch-size. Information on number of eggs is given for each species according to the mode, followed by the mean, the range, and the size of the sample.

4.--Distribution in Kansas. Information on distribution in the breeding season within the borders of Kansas is given in accounts below chiefly by reference to one or more counties of the State. Location of counties can be made by referring to Figure 10.

=Pied-billed Grebe=: _Podilymbus podiceps podiceps_ (Linnaeus).--This is a common but local summer resident, in and on ponds, marshes, streams, ditches, and lakes. The species can be seen in the State at any time, but usually arrives in the period March 1 to April 13 (the median is March 21), and departs southward in the period October 13 to November 18 (the median is October 24).

_Breeding schedule._--Nineteen records of breeding span the period May 1 to June 30; the modal date for egg-laying is May 15.

_Number of eggs._--Clutch-size is 4 to 10 eggs.

Nests are floating masses of marsh vegetation (cattail, smartweed, duckweed, filamentous green algae, and the like), kept green on top by addition of fresh material, in or at the edge of emergent marsh vegetation.

=Double-crested Cormorant=: _Phalacrocorax auritus auritus_ (Lesson).--This is a transient, but has been found nesting on one occasion in Barton County (Tordoff, 1956:311).

_Breeding schedule._--Eggs were laid in July and August in the one known nesting effort.

_Number of eggs._--Clutch-size is 2 to 4 eggs (Davie, 1898).

=Great Blue Heron=: _Ardea herodias_ Linnaeus.--This common summer resident nests in tall trees along rivers, streams, and marshes. The sector of greatest abundance is the Flint Hills. _A. h. herodias_ Linnaeus occurs in extreme northeastern Kansas, _A. h. wardi_ Ridgway breeds in southeastern Kansas, and _A. h. treganzai_ Court breeds in western Kansas; specimens showing intermediate morphology have been taken from the central part of the State. Occurrence in time, exclusive of the few that overwinter in Kansas, is shown in Table 10.

_Breeding schedule._--Seventy-seven records of breeding span the period March 1 to April 30 (Fig. 3); the modal date of egg-laying is April 5.

_Number of eggs._--Clutch-size is 4 eggs (4.4, 3-6; 36).

Nests are placed in crotches of sycamore, cottonwood, elm, hackberry, oak, and walnut, from 30 to 60 feet high; the average height is about 40 feet.

TABLE 10.--OCCURRENCE IN TIME OF SUMMER RESIDENT HERONS IN KANSAS

=Green Heron=: _Butorides virescens virescens_ (Linnaeus).--This is a common summer resident about streams, lakes, and marshes throughout the State. Some characteristics of the temporal occurrence of this species are indicated in Table 10.

_Breeding schedule._--Twenty-eight records of breeding span the period April 21 to June 20 (Fig. 3); the modal date of completion of clutches is May 5.

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The Breeding Birds of KansasChapter I: Part 1

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