Document Type

Dissertation

Date of Award

1977

Keywords

Bank swallow, Behavior

Degree Name

Doctor of Philosophy (PhD)

Department

Biological Sciences

First Advisor

John R. Haugh

Second Advisor

George J. Schumacher

Third Advisor

John J. Christian

Abstract

The bank swallow, Riparia riparia, is a common colonial swallow of the Northern Hemisphere. It nests in burrows which it digs in stream banks or in man-made excavations in sand and gravel banks. Colonies located in seven sand banks near Ellenville, New York, were studied.

Data were collected on 2,816 birds banded from 1965 to 1976 and on 246 birds that returned in subsequent nesting seasons through 1976. In addition, information on the development of the colony, nesting success, predation, and foraging was obtained during the nesting seasons of 1975 and 1976.

The first swallows to arrive at the colony site located their burrows in small groups high on the bank face. Succeeding burrows were begun over a period of 20 to 30 days in positions surrounding the first burrows and at distances from them. Banding and wing length data suggested that one year old birds arrived at the colony later than did the older birds. The younger birds obtained the outer and lower nesting locations.

Most of the young were produced in burrows from dense centrally located areas of the colony. Peripherally located burrows, started late in the nesting season, were generally less successful.

Clutch size in 170 nests was 4.38 ± 0.08 (mean ± standard error).

Bank swallows that started their burrows early in the nesting season took up to three weeks longer to complete the nesting cycle than did birds that started later. The mean length of time from the start of a burrow to fledging of young was 48.4 ± 0.14 days (N = 860).

Observations of predation suggested that predation was a disadvantage of coloniality in bank swallows. Mobbing of predators by adult swallows appeared to be ineffective.

Data on the direction of disappearance of adult birds as they individually flew off to obtain food for their young were recorded during 20 hours in 1976. These data showed that the food finding efforts of most birds from a colony were concentrated in one or two areas, and that the favored areas shifted over time. These shifts presumably correspond with local variations in the abundance of aerial insects. A system of communication of information on the location of food is proposed. The social facilitation of foraging is suggested to be an adaptive feature of coloniality in bank swallows.

A total of 11.2% of adult birds banded returned in a subsequent nesting season, as did 6.5% of the young birds banded. The return rate of males was not significantly different from that for females. More than two-thirds of the returning swallows nested again at the same colony location, and about one-third were recaptured at another colony site within a few miles from the banding site. Males were more likely to move to a new location than were females. Unsuccessful nesting and deterioration of the sand bank were believed to prompt relocation in a succeeding nesting season.

The oldest bank swallows in this study were at least six years old. The annual survival rate for adults as calculated from returns was 53% for males and 54% for females.

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