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
================+==========================+=============================
| 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=: _Nyctanassa 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.
=Least Bittern=: _Ixobrychus exilis exilis_ (Gmelin).--This is a local
summer resident in marshland. Characteristics of its occurrence in time
are indicated in Table 10.
_Breeding schedule._--Eleven records of breeding span the period May 21
to July 20; the modal date of egg-laying seems to be in the first week
of June.
_Number of eggs._--Clutch-size is about 4 eggs.
Nests are placed in dense emergent vegetation a few inches to a foot
above the surface of the water.
=American Bittern=: _Botaurus lentiginosus_ (Rackett).--This is a local
summer resident in marshes and heavy grassland. The species occurs
temporally according to characteristics as listed in Table 10.
_Breeding schedule._--Eggs are laid in May and probably in June.
_Number of eggs._--Clutch-size is 3 or 4 eggs.
Nests are placed on the ground in heavy cover.
=White-faced Ibis=: _Plegadis chihi_ (Vieillot).--This is a local summer
resident in marshland; actual records of breeding come only from Barton
County (Nossaman, 1952:7; Zuvanich, 1963; M. Schwilling, personal
communication, July, 1962). The species has been recorded in the State
from April 17 to October 6.
_Breeding schedule._--Twenty-five breeding records are for June and
early July.
_Number of eggs._--Clutch-size is about 4 eggs (3.9, 3-4; 24).
Nests are placed in emergent marsh vegetation near the surface of the
water, in Barton County in extensive cattail beds harboring also
Black-crowned Night Herons.
=Mallard=: _Anas platyrhynchos platyrhynchos_ Linnaeus.--This is a local
summer resident around marshes. The time of greatest abundance is
October to April, but most birds move north for breeding.
_Breeding schedule._--Fifteen records of breeding span the period April
1 to June 10; the modal date of egg-laying is in the first ten days of
May.
_Number of eggs._--Clutch-size varies widely; first clutches are of
about 12 eggs. Brood sizes vary from 3 to 12 individuals in Kansas.
Nests are placed on the ground surface, in pasture grasses, marsh
grasses, cattail, sedge, and smartweed.
=Pintail=: _Anas acuta_ Linnaeus.--This is a local summer resident in
marshland. The time of greatest abundance is from September to May, but
most birds move north for breeding.
_Breeding schedule._--Eleven records of breeding span the period April
21 to June 10; the peak of egg-laying seems to be in the period May 1
to 10.
_Number of eggs._--Clutch-size is around 10 eggs. Brood sizes vary
from 3 to 8 individuals in Kansas.
Nests are placed on the ground surface, in cover of marsh grass,
cattail, or sedge.
=Blue-winged Teal=: _Anas discors discors_ Linnaeus.--This summer
resident is locally common around marshes and ponds. The species arrives
in spring in the period March 9 to April 5 (the median is March 23);
birds are last seen sometime between October 7 and November 26 (the
median is October 20).
_Breeding schedule._--Twenty-two records of breeding span the period May
1 to May 30; the peak of egg-laying is around May 15. It is doubtful
that the present data indicate the full extent of the egg-season in this
duck.
_Number of eggs._--Clutch-size is 8 to 12 eggs.
Nests are placed on the ground surface, in cover of grasses, cattail and
sedges.
=Shoveler=: _Anas clypeata_ Linnaeus.--This is an irregular and local
summer resident, around marshes. Most individuals seen in the State are
passage migrants. Breeding records are from Barton and Finney counties.
_Breeding schedule._--Seasonal limits are unknown for the Shoveler in
Kansas.
_Number of eggs._--Clutch-size is about 8 eggs (Davie, 1898).
Nests are placed on the ground surface in cover of marsh vegetation.
=Wood Duck=: _Aix sponsa_ (Linnaeus).--This is an uncommon summer
resident around wooded streams and ponds in eastern Kansas. Nesting
records and specimens taken in the breeding season come from east of
stations in Pottawatomie, Coffey, and Woodson counties. Most nesting
records at present come from the Marais des Cygnes Wildlife Refuge, Linn
County. The species is present in the State from March 5 to December 8.
_Breeding schedule._--Eleven records of breeding span the period March
21 to May 10; the peak of egg-laying is probably in mid-April. The
present data are inadequate for showing the full span of the breeding
season.
_Number of eggs._--Clutch-size is around 15 eggs, varying from 10 to 23
in the sample at hand.
Nests are placed in crevices and hollows in trees near water, 10 to 70
feet high.
=Redhead=: _Aythya americana_ (Eyton).--This duck nested at Cheyenne
Bottoms, Barton County, 1962: 9 eggs found May 31 (M. Schwilling); also
reported to have nested at Cheyenne Bottoms about 1928 (Tordoff,
1956:316).
=Canvasback=: _Aythya valisineria_ (Wilson).--This duck nested at
Cheyenne Bottoms, Barton County, 1962: 14 eggs found June 20 (M.
Schwilling).
=Ruddy Duck=: _Oxyura jamaicensis rubida_ (Wilson).--This is a local
summer resident in marshland; numbers seem generally higher in western
than in eastern Kansas. The season of greatest abundance is March
through November, but numbers are conspicuously reduced in midsummer.
_Breeding schedule._--Eggs are known to be laid in May and June.
_Number of eggs._--Clutch-size is about 10 eggs (Davie, 1898).
Nests are placed near the edge of water, either in or on emergent marsh
vegetation; nests of other marshland birds, such as coots, are sometimes
appropriated (Davie, 1898).
=Turkey Vulture=: _Cathartes aura teter_ Friedmann.--This summer
resident is common throughout Kansas. Occurrence in time is indicated
in Table 11.
_Breeding schedule._--Fifteen records of breeding span the period
April 21 to June 10; earlier records will doubtless be found, to
judge from the frequency distribution of the present sample. The peak
of egg-laying is perhaps around May 1.
_Number of eggs._--Clutch-size is 2 eggs (1.8, 1-2; 12).
Nests are placed in holes and crevices in trees and cliffs, on rocky
ledges, and the like.
[Illustration: FIG. 3.--Histograms representing breeding
schedules of two herons, the Red-tailed Hawk, Bobwhite, and two
shore birds in Kansas. See legend to Figure 1 for explanation
of histograms.]
=Black Vulture=: _Coragyps atratus_ (Meyer).--This is possibly a
summer resident in the southeastern sector of Kansas. There is one
nesting record, for Labette County (Goss, 1891:245).
_Breeding schedule._--There are no data for this species in Kansas.
_Number of eggs._--Clutch-size is 2 eggs (Davie, 1898).
Nests are placed in hollows (logs, stumps, _etc._) on the ground
surface.
=Swallow-tailed Kite=: _Elanoides forficatus forficatus_
(Linnaeus).--This kite was formerly a summer resident in eastern
Kansas; it no longer occurs as a breeding species.
_Breeding schedule._--In Kansas the season seemed to occur relatively
late in the year for a raptor; eggs were laid in May, so far as is
known.
_Number of eggs._--Clutch-size is about 2 eggs (Davie, 1898).
Nests are placed in tops of trees.
=Mississippi Kite=: _Ictinia misisippiensis_ (Wilson).--This is a
common summer resident in southern Kansas, west to Morton County.
Specimens taken in the breeding season and records of nesting come
from south of stations in Grant, Barton, Harvey, and Douglas counties;
the present center of abundance is in Meade, Clark, Comanche, Barber,
and Harper counties.
_Breeding schedule._--Seven records of breeding span the period April
20 to June 10; the peak of egg-laying seems to be in the first week of
May.
_Number of eggs._--Clutch-size is 2 eggs.
Nests are placed about 35 feet high (from 25 to 50 feet) in
cottonwood, willow, elm, black locust, and the like.
=Sharp-shinned Hawk=: _Accipiter striatus velox_ (Wilson).--This rare
summer resident apparently occurs only in the eastern part. The two
nesting records are from Cloud and Pottawatomie counties.
_Breeding schedule._--The information at hand suggests the birds lay
in April and May.
_Number of eggs._--Clutch-size is about 4 eggs (Davie, 1898).
Nests are placed 20 or more feet high in coniferous or deciduous
trees.
=Cooper Hawk=: _Accipiter cooperii_ (Bonaparte).--This is an uncommon
resident. Specimens taken in the breeding season and actual records of
nesting come from east of stations in Cloud, Anderson, and Montgomery
counties.
_Breeding schedule._--Fourteen records of breeding span the period
March 21 to May 30; the modal date of egg-laying is April 25.
_Number of eggs._--Clutch-size is 4 eggs (3.8, 2-5; 5).
Nests are placed from 15 to 30 feet high, averaging 25 feet in elm,
oak, and other trees.