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° 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 watercourses; 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°F. or 30°F. in winter to 80°F. or 90°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.

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.

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).

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.