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 cla.s.s 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 ma.s.ses 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

================+==========================+=============================

Arrival

Departure SPECIES +----------------+---------+------------------+----------

Range

Median

Range

Median ----------------+----------------+---------+------------------+---------- Great Blue Heron

Feb. 4-Apr. 8

Mar. 20

Oct. 10-Nov. 29

Oct. 23 Green Heron

Mar. 29-May 4

Apr. 27

Sept. 1-Oct. 30

Sept. 9 Common Egret

Apr. 8-May 12

Apr. 2

Sept. 4-Sept. 30

Sept. 21 Black-crowned

Night Heron

Mar. 27-May 18

Apr. 25

Sept. 10-Nov. 11

Sept. 25 Yellow-crowned

Night Heron

Apr. 15-May 18

Apr. 27

American Bittern

Apr. 4-May 9

May 1

Oct. 6-Dec. 12

Oct. 16 Least Bittern

Apr. 9-May 22

Apr. 8

Oct. 24

----------------+----------------+---------+------------------+----------

=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.

_Number of eggs._--Clutch-size is 3 eggs (3.1, 3-5; 17).

Nests are placed about 10 feet high (two to 35 feet) in willow, cottonwood, elm, and the like.

=Little Blue Heron=: _Florida caerulea caerulea_ (Linnaeus).--This is chiefly a postbreeding summer visitant, but there is one record of breeding in Finney County (Tordoff, 1956:312).

_Breeding schedule._--There is no information on breeding schedule in Kansas or in adjacent areas.

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

Nests are placed in trees and bushes at various heights above the ground.

=Common Egret=: _Casmerodius albus egretta_ (Gmelin).--This is a postbreeding summer visitant, but has been found nesting once in Cowley County (Johnston, 1960:10). Occurrence in time is listed in Table 10.

_Breeding schedule._--There is no information on breeding schedule in Kansas.

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

Nests are placed in trees, usually above 20 feet in height; the one instance of nesting in the State was within a colony of Great Blue Herons.

=Snowy Egret=: _Leucophoyx thula thula_ (Molina).--This postbreeding summer visitant has been found nesting once in Finney County (Tordoff, 1956:312).

_Breeding schedule._--There is no information on breeding schedule in the State.

_Number of eggs._--Clutch-size is 2 to 5 eggs (Davie, 1898).

Nests in Kansas are placed among those of Great Blue Herons.

=Black-crowned Night Heron=: _Nycticorax nycticorax hoactli_ (Gmelin).--This is a locally common summer resident around marshes and riparian habitats. Characteristics of the occurrence of the species in time are given in Table 10.

_Breeding schedule._--Eggs are laid in the period May 1 to August 10.

_Number of eggs._--Clutch-size is about 4 eggs.

Nests are placed at medium elevations in riparian trees, in Kansas chiefly cottonwood, or in beds of emergent marsh vegetation.

=Yellow-crowned Night Heron=: _Nyctana.s.sa violacea violacea_ (Linnaeus).--This is a local summer resident in riparian habitats, chiefly in southeastern Kansas. Specimens taken in the breeding season and records of nesting come from Meade, Stafford, Doniphan, Douglas, Greenwood, Woodson, Labette, and Cherokee counties. Characteristics of occurrence in time in Kansas are shown in Table 10. _Breeding schedule._--Eggs are laid in May and June.

_Number of eggs._--Clutch-size is about 4 eggs.

Nests are placed in riparian trees.