HARVARD UNIVERSITY

LIBRARY

OF THE

Museum of Comparative Zoology

MUS. C3MP. ZSSSL LIBRARY

lihi'UiiilTY

THE

WILSON BULLETIN

A Quarterly Magazine of

Ornithology

Keith L. Dixon Editor

Editorial Advisory Board

George A. Bartholomew William A. Lunk

Kenneth C. Parkes Raymond A. Paynter,

Volume 68 1956

Published

by

THE WILSON ORNITHOLOGICAL SOCIETY

MUS. COMP. ZOOL LIBRARY

JUL 171959

HARVARD

UNIVERSITY

-W

MBS. COMP. ZO0L LIBRARY

JUL171959

UAJUAnn

March 1956

UNIV

RSITY

VOL. 68, No. 1 PAGES 1-88

®fje TOson pulletw

Published by

ie Wilson (^rnttfjologtcal ^>octetp

at

Lawrence, Kansas

The Wilson Ornithological Society Founded December 3, 1888

Named after Alexander Wilson, the first American ornithologist.

President Burt L. Monroe, Ridge Road, Anchorage, Kentucky.

First Vice-President John T. Emlen, Jr., Dept, of Zoology, University of Wisconsin, Madison 6, Wisconsin.

Second Vice-President Lawrence H. Walkinshaw, 1703 Central Tower, Battle Creek, Michigan.

Treasurer Ralph M. Edebum, Dept, of Zoology, Marshall College, Huntington 1, West Virginia.

Secretary Phillips B. Street, Route 1, Chester Springs, Pennsylvania.

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Wilson Ornithological Society Library The Wilson Ornithological Society Library, housed in the University of Michigan Museum of Zoology, was established in concurrence with the University of Michigan in 1930. Until 1947 the Library was maintained entirely by gifts and bequests of books, pamphlets, reprints, and ornithological magazines from members and friends of The Wilson Ornithological Society. Now two members have generously established a fund for the purchase of new books; members and friends are invited to maintain the fund by regular contributions, thus making available to all Society members the more important new books on ornithology and related subjects. The fund will be administered by the Library Committee, which will be happy to receive suggestions on the choice of new books to be added to the Library. H. Lewis Batts, Jr., Kalamazoo College, Kalamazoo, Michigan, is Chairman of the Committee. The Library currently receives 65 periodicals as gifts and in exchange for The Wilson Bulletin. With the usual exception of rare books, any item in the Library may be borrowed by members of the Society and will be sent prepaid (by the University of Michigan) to any address in the United States, its possessions, or Canada. Return postage is paid by the borrower. Inquiries and requests by borrowers, as well as gifts of books, pamphlets, reprints, and magazines, should be addressed to “The Wilson Ornithological Society Library, University of Michigan Museum of Zoology, Ann Arbor, Michigan.” Contributions to the New Book Fund should be sent to the Treasurer, Ralph M. Edeburn, Dept, of Zoology, Marshall College, Huntington 1, West Virginia (small sums in stamps are acceptable). A complete index of the Library’s holdings was printed in the September 1952 issue of The Wilson Bulletin. and each September number lists the book titles in the accessions of the current year. A brief report on recent gifts to the Library is published in every issue of the Bulletin.

The Wilson Bulletin

The official organ of The Wilson Ornithological Society, published quarterly, in March, June, September, and December, at Lawrence, Kansas. In the United States the subscription price is $3.00 a year, effective in 1951. Single copies, 75 cents. Outside of the United States the rate is $3.25. Single copies, 85 cents. Subscriptions, changes of address and claims for undelivered copies should be sent to the Treasurer. Most back issues of the Bulletin are available (at 50 cents each for 1950 and earlier years, 75 cents each for 1951 and subsequent years) and may be ordered from the Treasurer.

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Entered as second class matter at Lawrence, Kansas. Additional entry at Ann Arbor, Micb.

THE WILSON BULLETIN

A QUARTERLY MAGAZINE OF ORNITHOLOGY

Published by The Wilson Ornithological Society

Vol. 68, No. 1 March 1956 Pages 1-88

CONTENTS

Male Red-winged Blackbird, photograph by Robert W. Nero . facing p. 5 A Behavior Study of the Red-winged Blackbird

I. Mating and Nesting Activities Robert W . Nero 5

Fossil Birds of the Late Pliocene of Cita Canyon, Texas

Alden H. Miller and Robert I. Bowman 38 Measurements of the Habitat Niche of the Least Flycatcher

W. J. Breckenridge 47

The Rock Ptarmigan in Southern Baffin Island

George M. Sutton and David F. Parmelee 52 What Constitute Scientific Data for the Study of Bird Distri- bution? Josselyn Van Tyne 63

General Notes

INCUBATING AMERICAN ROBIN REPELS FEMALE BROWN-HEADED COWBIRD

Carl L. Leathers 68

goose-behavior by a white leghorn chick Peter H. Klopfer 68

CHANGES IN ENGLISH SPARROW POPULATION DENSITIES A. L. Rand 69

BEHAVIOR OF A RING-NECKED PHEASANT ON A PRAIRIE CHICKEN BOOMING GROUND

Elsworth M. Harger 70

altitudinal records for chimney swifts George G. Williams 71

NESTING OF THE MOUNTAIN BLUEBIRD IN CLEVELAND COUNTY, OKLAHOMA

Carl D. Riggs 72

THE PROTHONOTARY AND KENTUCKY WARBLERS ON COZUMEL ISLAND, QUINTANA

roo, Mexico Ernest P. Edwards and Richard E. Tashian 73

AN OLD NESTING RECORD FOR THE WHOOPING CRANE IN NORTH DAKOTA

Edmund A. Hibbard 73

BEHAVIOR OF PURPLE MARTINS WITH DISPLACED NESTS Ralph W . Dexter 74

AMERICAN EGRET FEEDING WITH CATTLE David K. Caldwell 74

BREEDING OF CASSIN’S SPARROW IN CENTRAL OKLAHOMA John C. Johnson, Jr. 75

Wilson’s petrel in southern Ontario Eric W . Bastin 76

PRAIRIE WARBLER BREEDING IN TEXAS 0. C. Sheffield 76

ROSE-THROATED BECARD NESTING IN THE CHIRICAHUA MOUNTAINS, ARIZONA

Robert H. Gibbs, Jr., and Sarah Preble Gibbs 77 goshawk captures American crow Louis J. V erme 78

Ornithological News 79

Conservation Section: Some Thoughts Concerning the Introduc- tion of Exotic Game Birds Robert A. Pierce 80

Ornithological Literature 83

Alexander Sprunt, Jr., North American Birds of Prey, reviewed by Kenneth C. Parkes; Ludlow Griscom and Dorothy E. Snyder, The Birds of Massachu- setts, reviewed by Aaron M. Bagg; Lyle K. Sowls, Prairie Ducks, reviewed by Clarence Cottam; Raymond A. Paynter, Jr., The Ornitho geography of the Yucatan Peninsula, reviewed by Keith L. Dixon.

Male Red-winged Blackbird ( Agelaius phoeniceus ) engaged in “song-spread” display. Photographed by Robert W. Nero, near Madison, Wisconsin, on

May 15, 1955.

A BEHAVIOR STUDY OF THE RED-WINGED BLACKBIRD1

I. Mating and Nesting Activities

BY ROBERT W. NERO

his study is concerned with the behavior of the Red-winged Blackbird

| or “Redwing” ( Agelaius phoeniceus ) on a breeding ground near Madi- son, Wisconsin, during the years 1948 through 1953. Part I describes the behavior related to pair formation, courtship and mating activities. The formation, maintenance, size, and structure of the male territory, female territorial behavior, and behavior of first-year (immature) males will be described in a subsequent issue of this journal. The study is a continu- ation and expansion of a more general study of this species initiated in the same area by James R. Beer in 1945 (Beer and Tibbitts, 1950) and is part of a thesis submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Zoology at the University of Wisconsin (one aspect published previously: Nero and Emlen, 1951).

Grateful acknowledgment is tendered Professor John T. Emlen, Jr., who offered advice and guidance throughout the study. Thanks are due the following persons for aid in various ways: Professors Robert A. McCabe and Joseph J. Hickey; Drs. James R. Beer, Ernst Mayr, Nicholas E. Collias, Ruth L. Hine, Howard Young, Arnold Bakken, Arnold Petersen, Robert L. Strecker, Fred A. Ryser, Frederick Greeley; Mr. Jack Kaspar, Mrs. L. S. Miller, and Miss Margaret Grismer. I wish to give special thanks to my wife, Ruth F. Nero, for her constant support during the years of graduate study. This study was aided by a Louis Agassiz Fuertes Research Grant awarded by the Wilson Ornithological Club in 1952.

Methods

The main study area was a 2.4-acre cattail \Typha) marsh on the east shore of Lake Wingra in the University of Wisconsin Arboretum at Madison. This marsh is bordered by red osier dogwrood and w illow, and is surrounded on three sides by a fairly dense stand of mixed hardwoods. Observations were also made at a feeding and flocking area in Vilas Park Zoo, about one-half mile north of the marsh. Additional records were obtained wher- ever Redwings were encountered.

Field notes were recorded on 358 days during six breeding seasons, from 1948 through 1953. (Supplementary notes were made in 1954 and 1955.) Observations began each year with the arrival of the first resident males in March and continued until August or September when resident birds (marked) left the area. Most of the photographs were taken by the author

1Journal Paper No. 32, University of Wisconsin Arboretum.

D

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THE WILSON BULLETIN

March 1956 Vol. 68, No. 1

in April and May, 1955, on several marshes within eight miles of Madison. I he photos in Figure 3, however, were taken in July, 1955, in Saskatchewan, Canada, with the aid of Mr. Fred W. Lahrman.

Trapping of adults and immatures was accomplished by means of wire- mesh. treadle-sprung traps baited with white bread. These traps were placed on top of muskrat houses and floating boards, and on top of wire screens which were pressed onto old, standing cattails. Several females were cap- tured by placing a screen-bottomed trap directly on top of the nest when the female had a full set of eggs or young. Individual identification was obtained by the use of combinations of colored plastic “leg” bands. A drop of Duco cement applied within the plastic coil secured the band. From 1948 through 1952, 282 birds were so marked, 175 of these being juveniles. Observations were made with the aid of binoculars from several vantage points within the area as well as along the edge. In 1949 observations were greatly aided by watching from a board fastened between two trees on the edge of the marsh, about 12 feet above the water. This worked so well that in 1950 two towers 12 feet high were erected in the marsh. These elevated platforms permitted close observation of behavior ordinarily con- cealed by the vegetation.

The Birds

Size of population. The number of adult males holding territories on the study area during the height of the season (middle of April to middle of June) ranged from about 17 to 25 during the years 1948 through 1953. The number of females with nests during the same period ran from 27 to 50.

Dates of arrival and last appearance. From 1949 to 1953 previously- resident males (8 to 13 marked males each year) first appeared between March 6 (1950) and March 17 (1952) (average, March 10-11). The last ones to arrive appeared between March 22 (1953) and April 21 (1949). The minimum period for arrival of all the marked residents was 9 days (1953, 9 birds); the maximum, 43 days (1950, 13 birds). The average arrival period was 29.2 days. Certain males were consistently early arrivals, others consistently late. First arrival dates for individuals varied in con- secutive years over a period of up to 20 days (average, 13.6 days). Previously-resident females arrived first on April 8 (1952), April 16 (1951), and April 17 (1950). Information on dates of last arrivals of females is available only for 1951, in which year the last marked bird appeared May 7. I his gives a period for arrival of females that year of 21 days.

Very few marked birds were seen on the marsh in August, but some were seen on the feeding grounds at Vilas Park during this month. In 1948 a resident female and her young were still on the marsh on August 4;

Robert W. Nero

REDWING BEHAVIOR

7

they appeared to be the last birds present. On August 15 of the same year a marked adult male was seen at the park. A banded young was seen on the marsh on August 6, 1949. Evidence that at least some of the local residents do not migrate until later was obtained in 1951 when two marked adult males were seen on October 22 and 23, respectively, three miles from the breeding marsh. Each male was with a flock of about 50 males.

Annual returns. Fifty-six per cent of 50 marked adult resident males returned at least once during the period from 1947 to 1953. Each season, from 10 to 22 adult males were present (see Table 1). Marked resident females showed a similar rate of return. Of 48 birds, 56.2 per cent returned at least once during the seasons 1949 to 1953. Table 1 shows the survival of each year’s marked population. Of 16 different males, 10 survived five years, three survived six years, and three survived seven years. (Note: two 8 year olds returned in 1954 and a 9 year old bird returned in 1955.) Two females survived at least six years. Some of these birds were banded as adults and may have been older. Davis (1953) reports a life span of 15 years in captivity for the Cuban Redwing, A. p. assimilis.

Polygyny. Polygyny in the Redwing has been recorded by several authors (Allen, 1914:92; Roberts, 1932:306; Linsdale, 1938:140-141; Mayr, 1941:83), although a few observers have reported this species to be

Table 1

Yearly Return of Marked Resident Redwings

The lop number in each vertical column is the number of new residents marked that year. Reading down each column one sees the subsequent return of each year’s population.

Males

Year

1947

1948

1949

1950

1951

1952

1953

Total Population

1947

11

11

1948

7

10

17

1949

5

5

12

22

1950

2

3

8

7

20

1951

2

2

5

5

7

21

1952

1

1

1

2

3

4

12

1953

0

0

1

2

3

4

0

10

Females

Year

1949

1950

1951

1952

1953

Total Population

1949

15

15

1950

12

32

44

1951

5

14

2

21

1952

2

9

0

0

11

1953

0

9

0

0

0

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March 1956 Vol. 68, No. 1

monogamous (Williams, 1940:268; Mdlhenny, 1940:85). Redwing matings in this study were occasionally monogamous but were mainly polygynous. Of 25 males for which accurate records were kept, five had one mate each, 16 had two mates each, and four had three mates each. I have no record of a male breeding successfully with more than three females. However, in at least one case where a male had three mates, one female returned for a second nesting, so that four broods were brought off in this territory. Linsdale ( loc . cit.) working with unmarked birds in Nevada, reported that one male “. . . would have as many as 6 females all actively nesting.”

According to Linsdale {loc. cit.), “The success of a male in obtaining females in its territory seemed to depend almost entirely upon the suitability of the habitat for nest locations.” My females showed a preference for nesting on the edges of the openings within the dense cattail stands. Since not all territories had an equal amount of edge, some might have been more suitable for nesting than others. Linford (1935:37) found that the territories of polygynous Redwing males were twice the size of those of monogamous males, but I found no relationship between territory size and the number of nesting females. In Linford’s study, however, the birds obtained tfye bulk of their food within their territories, whereas my birds obtained most of their food outside their territories.

Allen (1934:136) considered that the male Redwing was not “agreeable” to polygamy because of the great difficulty of running two or three double families each season. He suggested that a male was “satisfied’" with one female. However, the males in my study played little part in feeding the young and only a very few birds (three! had more than one brood. Female intolerance of other females may play a large part in limiting the number of females breeding in one territory; a male is rarely able to successfully “court two females at exactly the same time. Nesting data tend to support this - in most, but not all, cases females w ithin a single male’s territory are “out of phase” with each other (see Table 2).

Second nesting. As Beer and Tibbitts suggested (1950:731 double broods are uncommon in the Redwing in this area. Only three cases of double broods were recorded in this study I in 1949, all successful!. In 1950. the year for which the most data are available, 20 marked females had suc- cessful first nests, but none of these females returned to the marsh for a second brood. In each case in which females had second broods, they bred with their original mates. A female which arrived on April 17 had fledged young on June 8, and nine days later she had her first egg in her second nest. Another female which left with her young on June 15, returned on June 28 and had her first egg on July 4, seven days later. A third female was feeding her fledged young until June 27 and on June 28 had her first

Robert W. Nero

REDWING BEHAVIOR

9

Table 2

Nesting Stages of Female Harem Mates in Seven Male Territories on June 7, 1950

Territory

Female 1

Female 2

Days apart

A

young at 2 days

young at 3 days

1

B

3 eggs

young at 6 days

6

C

3 eggs

young at 5 days

25

D

2 eggs, young at 1 day

young at 4 days

3

E

4 eggs

young at 3 days

12

F

3 eggs

young at 7 days

7

G

4 eggs

2 eggs, young at 2 days

2

egg in her second nest. In two of the above cases the pairs were never separated, the females remaining on or near the territory while feeding the young.

Prominent Displays and Postures

The behavioral characteristics described below include sexual, aggressive, and social posturings. Other sequential displays which are neither as well- defined nor elaborate are discussed under various sections (see Courtship and Copulation). Vocalizations are not completely covered in this study.

Exposed epaulets. Exposure of the patch of red feathers on the male’s wing is a generalized display seen on many occasions, usually in conjunction with other postures or movements. At higher levels of intensity the red coverts may be erected and even vibrated, thus greatly increasing their area and color effect. When a hawk is overhead, when a male trespasses on another territory or is being dominated, or when a male is feeding together with other males on the ground, the red coverts are kept concealed.

Male song-spread. “Song-spread” designates the behavior of the Redwing during the delivery of the well-known “oak-a-lee” song. Variations of the male display may be seen in Figure 1 (a, 6, c, g, h, i) . Usually the head is lifted or thrust forward, the tail is spread and lowered, the wings are spread, and the epaulets are raised (see Figure lg, h) . The head is thrust out with the first note of the song; at the climax, the drawn-out “lee,” the tail and wing feathers are carried to the extreme position. The closure of song usually marks the return to normal position, but often the spread display is held for some time afterwards. The extent of song-spread, and other displays, varies with the level of motivation. In extreme or “complete” displays the wing-tips touch the outer tips of the tail, the bird sometimes assuming an almost disk-like form (Fig. 1 h. i) . The last phrase of the song is similarly given with varying emphasis. According to Allen (1914: 89) the song “. . . is always accompanied by spreading of the wings and tail feathers and by erection of practically all the body feathers, especially

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those of the shoulder patches.” However, this song is sometimes given with little plumage display (Fig. la).

Song-spread is given commonly on the territory but it is also frequently given off the territory and before and after the breeding season, though generally without the postural components. Migrating Redwings are in constant song, especially on the roosting grounds. Although song is often given by solitary males, it is given with a greater frequency and extent in the presence of other males. It appears most extensive when directed toward a particular individual. Song is most frequently given while the male is perched but it is also given while in flight. It may at all times, however, be readily distinguished from the “flight-song” described below. Song- spread is given on the territory long before the females arrive, and although it may be given more frequently and extensively in the presence of a female, it appears to be directed mainly toward other males. The presence of a female seems simply to elicit a greater amount of “warning” song.

Female song-spread. A song-spread display resembling that of the male is commonly given by females (note comparable postures in Figure 1). As in the male, the degree of posturing changes with the intensity of the display. In the “complete” display the bird stands upright, with head raised, tail spread and lowered, with the red-tinged epaulets sometimes erected. The female song, although given with considerable variation, is generally a series of high, shrill and rapid notes, slowing and descending at the end, the last phrase often very sibilant and slurred. It may be rendered “spit-a-chew- chew-chew . . .” or “check-check-a-skew-skew-skew. . .” A more halting and labored call “pee-chee-ta-chee-ta-chee-chee-chee . . .” often leads into the former call and seems to be a more general excitement or alarm call. Song-spread of the female usually is given to other females from prominent positions within her area. Often most of the females present on the marsh may be shrilling or screeching in song-spread to a single female circling overhead. In early May these calls sometimes seem to be the main sound on the marsh, almost eclipsing the songs of the males. Female song-spread has been heard on the study area as early as April 8 (1952), one day after the first females had made their appearance.

Male flight-song .- “Flight-song” is a display given by males which often serves to distinguish territorial birds, although it is given less frequently than song-spread. The full call, always given in flight, is a long, rapid series of notes something like: “tseeee . . . tch-tch-tch-tch . . . chee-chee- chee-chee . . .”, (the middle phrase often very nasal in tone, sometimes

Fig. 1 < opposite page) Song-spread display, male and female. All photos taken at height of display, and the figures are arranged to show increasing intensity of display. Note comparable postures of the two sexes.

Robert W. Nero

REDWING BEHAVIOR

11

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“tank”). Sometimes only a portion of the call is given, and often the number of notes in each phrase varies, but the call is very distinctive.

What is apparently the same display is mentioned by Allen (1914:90) : “. . . a sort of scolding song, which is given in the air, with quivering wings, can easily be resolved into: check, check, check, t’tsheah .” The

“flight song” described by Beer and Tibbitts (1950:67) may be the same thing: “The victory display or flight song ... is normally given after successfully chasing a trespassing male from the territory. After the chase has been completed the male slows his wingbeat, spreads his tail and ‘para- chutes' back to his singing perch. During this display he is in continuous song.” I have only occasionally observed this display as an aftermath of an aggressive chase. It is regularly given when leaving or returning to the territory, the return flight often being a long, slow glide.

A rapid call which resembles the middle phrase of the flight-song (“tch- tch-tch . . .”) is frequently given during sexual chasing, where it appears to be a scolding or vocal threatening. A similar call was heard on other occasions also suggesting an aggressive motivation. For example, on May 21, 1950, a male gave it repeatedly while chasing a Kingbird (Tyrannus tyrannus ) .

Bill-tilting. Beer and Tibbitts (1950:67) described a posture assumed by males in mutual threat on their territory boundaries which they called the “bluff" or “stretch display.” A closely similar display has been observed in several other icterids. For example, Williams (1952:8 ) called a probably- related display in the Brewer’s Blackbird ( Euphagus cyanocephalus ) the “head-up display.” Since the most constant characteristic of this display in the Redwing appears to be the raised beak, I have called it “bill-tilting.” Prominent aspects of this pose are the stretched neck with raised beak and compressed body plumage (see Figure 2a, 6). Although the epaulets are exposed in this display, they are never erected. Bill-tilting is most commonly given by adult males on their territory boundaries, each moving up, when suitable perches are being used, as if one bird were attempting to avoid the other without giving ground. On one occasion when two males were tilting to each other in a tree, the uppermost bird moved down and even hung down to display to the lower bird as the latter moved up. It is also given by females I Fig. 2c), immatures and young. It is mainly an intraspecific display, but both males and females have been observed to give it when confronting other species of birds. Females commonly used it in threat to other females (Fig. 2d), occasionally to first-year males, and rarely to adult males. Juveniles used it mainly against first-year males. On several occasions aggressive action was observed immediately following bill-tilting.

Male crouch .- The “crouch” is a tense crouching posture assumed by the

Robert W. Nero

REDWING BEHAVIOR

13

Fig. 2. Bill-tilting display, male and female.

male while perched (see Figure 4a). The body is depressed, the head is hunched and held low, the tail is spread and brought downward, and the “shoulders” are held out from the body with the epaulets erected. The wing tips may be crossed over the back or dropped close to the sides. Rarely, the spread tail is momentarily raised. (Males also occasionally held their tails nearly straight up in evident alarm, but nothing comparable to the “elevated tail display” described by Williams (1952:7—8) in the Brewer’s Blackbird was seen in the Redwing. Flocks of Redwing males feeding on the ground often keep their tails lifted, a gesture not at all understood.) The crouch posture often is assumed by the male when near one of his mates, usually while facing her, and often preceding further sexual activity. It is also given before new females and before dummy females, but it has not been seen otherwise. Apparently it is an indication of sexual interest.

Female wing-flipping. During the period of “feeding-the-young” the female frequently raises and flips one or both wings when her mate is

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Fig. 3. Female wing-flipping display.

nearby. Such “wing-flipping” involves movement of the whole wing at body level, and, at high intensity, nearly vertically (see Figure 3). In some cases the wing on the side toward the male was held highest. This behavior is apparently not accompanied by any vocalization, but in two cases females held their beaks open. In one instance a female repeatedly bowed “as if to touch her beak to water to drink” and increased her wing-flipping (higher and faster) as her mate approached. Finally the male dived at her aggressively.

Wing-flipping was observed to be given as much as 10 feet from the nest, although it was usually seen at a lesser distance. It was given especially just after a return to the territory with food for the young, and shortly before departure for more food. In one case a female flipped her wings before feeding her young and then kept them raised while actually feeding them. In all of 20 detailed observations of wing-flipping recorded between June 7 and July 16 (1950) the females had young in their nests ranging from one to eleven days old. The mate was always nearby when the female wing-flipped. On a few occasions both male and female have been observed to give a kind of wing-flipping when leading young off the marsh.

One female, whose nest had been transported experimentally into a strange territory, upon being attacked at her nest site by the resident male, raised

Robert W. Nero

REDWING BEHAVIOR

15

a wing on the side away from the male as if in defense. At this time she had eggs in her nest. This is the only instance in which a female with eggs raised a wing to a male. Two days later when the eggs had hatched she raised and flipped both wings to the same male. At the Vilas Park feeding grounds several observations were recorded of females lowering a wing to the ground when being approached aggressively by adult males. The latter usually appear antagonistic to strange females on the feeding grounds. In one case when a female was threatened by an adult male she raised and fluttered her wings at her sides in the manner of a young bird begging for food. The above actions by females appeared to be defensive reactions. According to Nice (1937:57), male Song Sparrows ( Melospiza melodia ) attempting to invade a territory often held one wing straight up in the air and fluttered it as they faced the defending resident male. In one unusual case when a female (which sometimes drive off trespassing males) faced a trespassing male she was “. . . all puffed out and flipping a wing . . .” at the male (Nice, 1943:187).

A unique observation was made on an unmarked pair of birds on June 22, 1950, at a lake 30 miles from the study area. A male was seen approaching a female which was perched near a nest. The female began slowly flipping both wings quite high and then, apparently coincident with signs of sexual excitement in the male, she lowered her wings, fluttered them more rapidly and went directly into precopulation display (see Figure 4 h) , quivering her wings and raising her tail slightly. The male soon dropped his excitement postures, but the female maintained hers for a few seconds later.

These observations under normal conditions were supplemented by obser- vations in Saskatchewan in 1955 during an experimental attempt to elicit wing-flipping behavior for photographic coverage (see Figure 3). On July 16 five newly-fledged young were placed in a small cage which was set about 12 feet from the camera. For l1^ hours the female attempted unsuc- cessfully to feed her young, meanwhile giving extensive wdng-flipping before the thoroughly-alarmed male. The female frequently raised both wings, often holding the one of the side toward the male higher, and rapidly reversing wings when she changed position. Much of this sequence was suggestive of the behavior of fledglings begging for food (see Nice, 1950:89). The female continued to show wing-flipping as she searched for food as much as 50 feet from the young and the male, but her wings were held highest when the male was near. Sometimes one wing would be raised over her back and tilted over the opposite side (see Figure 3c, d) . When her wings were held up and shaking, her posture resembled the “elevated wings” of the courting male (Figure 4c). In extreme display her wings were raised over her back until they touched and were then directed toward the male, some-

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times by tilting or bowing. The male seemed to show some aggression to the female at this point and once raised his wings while pecking toward his displaying mate.

Wing-flipping by the female seems to be an indication of her concern with “feeding-the-young.” Just as the male simulates female nest-building be- havior during courtship (see Symbolic Nesting) and in moments of anxiety during that stage of their .cycle, so the female simulates the behavior of hungry young.

The Pairing Bond

In the Redwing, as in the majority of passerines, the sexes form a bond for the breeding period only. In many species the members of the pair remain together until the young are self-sufficient, but Redwings appear to separate as soon as the female leaves the territory with the young. This must be the case when the male remains on his territory with his other females, but even monogamous pairs apparently separate. Individuals of either sex have been observed caring for young off the territorial grounds, but I have never observed a marked pair together caring for their young off of the male’s territory, or at least very far from it. The pairing bond evidently lasts only while the pair is attached to the territory. I made many unsuc- cessful attempts to observe breeding pairs feeding together outside their territory. Mated pairs only infrequently left the marsh together to feed (the male usually returning first), although males often left in small groups and these birds sometimes fed close together.

In the Redwing the pairing bond does not appear to carry over from season to season as it does in the Brewer’s Blackbird (Williams, 1952:9—11). Several of my returning females remated with their former mates but others mated with other males even though their previous mates were present. Nevertheless, females which reassociated with former mates seemed to estab- lish themselves with less effort than did those which acquired new mates.

In Redwings it is well-known that the sexes tend to remain separate throughout the non-breeding season. Males revert to flocking behavior as soon as they quit their territories. My marked males were often seen associ- ating together with other adult males on the Vilas Park feeding grounds in late July and August. In one unusual case a male cared for two of his young until they were 36 days old; during the last nine days of this period he was observed on the feeding grounds in loose association with a flock of males. Females also flock together at this time and move to the uplands with the majority of the young.

Fic. 4. (opposite page) Sexual displays, male and female. Figs, cr-c: male “court- ship”; d-e: male precopulation; f-k: female precopulation, showing increasing intensity.

Robert W. Nero

REDWING BEHAVIOR

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18

THE WILSON BULLETIN

March 1956 Vol. 68, No. 1

Arrival and Establishment of Females

Arriving females are generally fairly quiet and may only give soft “check” or “prit” calls. Single birds or small groups circle in the air over the marsh, or perch nearby and sit quietly or give frequent tail flips until approached by males. Usually the appearance of a new female alerts the males within several hundred feet and various short calls, such as a “check” or soft “ticka-ticka” or shrill “tseee” are given. Some males may sing and fly down to their respective territories; some may stay up on their perches; others may fly up and perch near a female. If a female remains up in a tree, then the males, perhaps several of them, fly up and perch near her, slowly hop along the branches toward her (usually with erect epaulets), and then fly down with song-spread to their territories. Often the females flee at the approach of the males; the latter sometimes fly after them for several hundred feet before returning to their territories. Sometimes these females circle the marsh before flying away and occasionally they suddenly dive into the cattails.

When a female lands in the cattails all the males nearby usually move up to their borders nearest the female and perform a song-spread broadly (Fig. lg, h, i) . The holder of the territory on which the female lands often approaches to within a few feet of her to do this and then displays for several seconds after the cessation of song (Fig. 46). This “after-song” pose is sometimes accompanied by a soft-whimpering “ti-ti-ti-ti-. . On some occasions males held their wings spread before they sang. At this time there may be comparatively little song from the holder of the territory. If the female approaches the male he sometimes drops down to the base of the cattails, often down onto the early spring ice, and struts around with wings extended laterally, sometimes rapidly vibrating them, while giving the call mentioned above. Sometimes the extended wings may be partly raised. This display was also given immediately after song-spread with the male perched on the cattails. A similar posturing was observed when males approached a female dummy. In repeated observations of this display before a dummy, the males walked rather stiffly with raised rump feathers and lowered head, occasionally pausing to rest or to give song-spread. This display is similar to part of the male precopulatory display (Fig. 4</, e). It may be considered an indication of a high level of sexual excitement.

Similar displays were also given on several occasions to other males early in the season before any females had arrived On March 6, 1951, an adult male at least three years old repeatedly held his wings outspread and quivering while giving the “ti-ti- . . .” call. This display was given alter- nately with full song-spread and erect epaulets to approaching flocks of male Redwings, as well as to approaching individuals, including one first-year

Robert W. Nero

REDWING BEHAVIOR

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male. From March 12 to 27, 1952, several different males were observed giving this display to other males. It seemed especially to be directed by residents toward new males, which often came in without song and w*ith epaulets more or less concealed. These observations suggest that responses in the male which are normally geared to the female may be set off momen- tarily by movements or postures in other males which in part resemble or are suggestive of female characteristics. However, this does not imply an outright failure of sex-recognition.

Females sometimes flew in quietly and remained perched near males without making any apparent sound or motion, appearing quite relaxed. Although these females might evoke a display in the male they sometimes flew7 away quietly afterwards without being chased. Established females occasionally flew into the marsh without arousing any special interest from the males which were apparently able to recognize them as one of their own or a neighbor’s mate. In many cases formerly-resident females appeared to arrive at the marsh late in the evening after most activities had ceased. A few' which were actually observed dropped right down into the cattails with little hesitation. These females were often found within an hour after sunrise the next morning sitting quietly on a male’s territory, behaving like established females, i.e., they stayed on the territory and sang to passing females. Some females showed much “tail flashing,” that is, rapid spreading and closing of the rectrices, sometimes accompanied by slight movement of the primaries. (This occurs in both sexes, but is especially prominent in females). Rarely, females visited several territories before finally settling in one, even though they sometimes had remained for several days in one territory. This was regarded as very unusual behavior since ordinarily if a female remained for one day in a male’s territory she kept that position. Females which were probably transients (or young?), however, often visited several territories in rapid succession.

Once a female has settled on a male’s territory and has become paired she may receive little attention from him, particularly if she remains low in the cattails and quiet. However, her quarrels with other females settling within the territory nearly always bring forth aggressive interference by the male. At times the female follows the male around as he shifts about in territorial defense. She may alight a few7 feet from him and slowly move toward him, upon which the male usually retreats. The newly-established female may also move toward an adjacent male in the same way for a few days, but in this case she is apt to draw an aggressive response from which she retreats. At other times the male shows an interest in his mate by diving at her, by giving various displays near her, and by sometimes following her off the marsh. Occasionally males followed their females as