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The Tree Swallow is one of the most familiar and most common birds in eastern North America. While it normally nests in tree cavities excavated by other species like woodpeckers, it also readily accepts nest boxes. Along with its abundance, this feature makes the Tree Swallow a favourite species for biologists to study on its breeding grounds.
Through Bird Studies Canada, Long Point Bird Observatory monitors three nest box “colonies” of Tree Swallows at Long Point, two on the “mainland” near Port Rowan (at the Port Rowan sewage lagoons and adjacent to agricultural land at Mud Creek) and the third at the Tip of the Point. Each colony contains 50-65 nest boxes.
In May through June, volunteer research assistants check nest box contents daily, weigh eggs and young, and band the adults and the young. The amount of food available to the swallows at each site is measured every day with specially-designed suspended nets that sample the abundance of flying insects. Twice-daily weather records are also collected at each site.
The objectives of this project are (1) to provide a long-term record of breeding performance of Tree Swallows in relation to their food supply and climate, (2) to provide other opportunities for research on breeding swallows, and (3) to provide training in field ornithology for students and other volunteers.
The Long Point Tree Swallow project has a superb set of data relating food abundance and weather conditions to breeding performance at 3 sites, extending over a 22-year period. This provides a sound basis for research on a variety of topics. Here are some results from Tree Swallow research at Long Point:
• Egg laying occurs later in cold springs and is usually 3-5 days later at the Tip of Long Point than on the mainland, because the proximity of Lake Erie results in cooler spring temperatures at the Tip.
• The number of eggs laid (clutch size, usually 4-7 eggs) by female Tree Swallows depends on the abundance of insects available to them prior to laying.
• Many adult swallows return year after year to the same site, sometimes to the same nest-box, and some of their young also return.
• Few Tree Swallows live more than six years, but one female banded at the tip of the point lived for 11 years. She bred at Long Point in at least 10 years from 1970 to 1980. She held the world record for Tree Swallow longevity until 1998 when a 12 year-old male was found at the Sewage Lagoon.
• Young Tree Swallows grow faster at the Lagoon, where insects are more abundant than at other sites where food is scarce.
The first Tree Swallow studies at Long Point began at the Tip of Long Point in the late 1960s. Geoff Holroyd conducted his Ph.D. research (University of Toronto) on resource allocation in swallows, Purple Martins and Eastern Kingbirds in 1970-74. At the same time David Hussell did postdoctoral research on relationships between insect abundance and parental care in Tree Swallows. Diane DeSteven (University of Michigan) studied effects of brood size and female age on reproductive success in 1975-76. The current program of monitoring performance in relation to food abundance at three sites began in 1977. In 1980-84, Terry Quinney conducted Ph.D. research (University of Western Ontario) and postdoctoral research, which mainly involved comparing breeding performance at two mainland sites with different food abundances. In 1982-84, David Hussell did research on parent-offspring food-provisioning interactions.
Recent Activities and Results, 1997-1999
After 3 decades of research, we can still say that each year has something new and different to offer. Despite the looming prospect of climate warming, 1997 proved to be the latest year on record, with no eggs laid until 18 May. By contrast, 1998 and 1999 were the earliest ever with the first eggs laid on 8 May in both years.
A pattern that seems to be emerging is that the delay between clutch initiations at the mainland sites and the tip of the point is greater in early seasons than in late ones. Median date of first eggs laid (by females at least 2 years old) was only 2 days later at the tip than on the mainland in 1997, but was 5 and 7 days later in 1998 and 1999, respectively. Presumably the cooling effect of the lake at the Tip of the point moderates the impact of early warm spells that stimulate early laying.
In 1998, a cold spell in early June reduced insect abundance and adversely affected many broods that were 2-8 days old at that time. A few nestlings died, but the biggest effect was retardation of flight feather growth in the survivors. Body weigh subsequently returned to normal, but there was no “catch-up” in feather growth. Consequently fledging was unusually late and some broods remained in the nest boxes until 22 days of age (versus about 18 days normally). Still, the young appeared to be in good condition at fledging time, so the ability to retard growth and remain longer in the nest appears to be an adaptation to a variable food supply.
In 1999, females laid more eggs at the Tip (mean 5.93, N=58) than at the Sewage Lagoon (mean 5.82, N=38) or Mud Creek (mean = 5.25, N=49). For the third year in succession, clutch sizes at the Lagoon averaged lower than at the Tip. This is very unusual, and is indicative of a crash in insect abundance at the Lagoon, which is reflected in our daily insect catches. Formerly, the Lagoon was consistently the most productive site with clutch sizes averaging as high as 6.4 in some years.
There were no major weather events in 1999, and productivity was generally high. Drs. Stephen Yezerinac and Robert Montgomerie, Queens University, investigated the relationships between plumage colour, mate choice and reproductive performance at the 2 mainland sites. Since birds can see ultraviolet light, they see the world and each other differently from humans. Plumage colour was measured on adults with a field spectrometer. Blood samples were taken from adults and young for DNA analysis. Previous work elsewhere has shown that some brood members result from extra-pair copulations (i.e. the eggs were fertilized by another male). The DNA analyses will show whether the same pattern exists at the LPBO sites and will indicate whether plumage colour is related to ability to obtain and/or prevent extra-pair copulations.
Also in 1999, David Hussell ran a series of experiments to try to determine whether the visual component of the brood’s begging signals contributes to stimulating adults to bring food to their young. It has long been known that the begging calls of the young stimulate parental feeding, but the role of the visual signal remains unclear. These experiments involved videotaping 9 and 12 day-old broods in a specially designed nest box.
Tree Swallow Banding
One component of the Tree Swallow program is to band all adults and young each year (about 1000 swallows annually). All of these banding and recapture data have recently been computerized, with a view to conducting analyses of survival and inter- and intra-area movements.
The banding has led to some interesting discoveries. For example, on 3 July 1998, volunteer Susan Anderson trapped a male swallow at Lagoon nest box # 30 that had been banded as a nestling at box #44A (about 49 metres from the recapture site) on 14 June 1986. It had hatched on 1 June 1986, so it was 12 years and 32 days old when recaptured in 1998. This is a new world record for longevity in the Tree Swallow!
In 1999, Charles Francis and David Hussell analyzed site fidelity of Tree Swallows, using 14,400 bandings of nestlings and 6,300 bandings and recaptures of adults accumulated from 1977 to 1998. They presented a poster paper describing their results at meetings of the Society of Canadian Ornithologists (Montreal) and the American Ornithologists’ Union (Ithaca, New York), and at the 100 Years of Bird Ringing Conference (Heligoland, Germany). They showed that about 61% of males that bred at a site and returned in the following year occupied the same nest box in both years, but only 29% of females did so. Also, males that occupied a different nest box moved a shorter distance than females that moved. Overall, males tended to be more site-faithful than females.
How to Get Involved
The Tree Swallow project is coordinated for LPBO by Dr. David J.T. Hussell. He welcomes inquiries from people who may wish to volunteer one or more weeks of their time in May or June to assist with the swallow project. Tree Swallow assistants also usually have opportunities to be involved in LPBO’s migration monitoring program in May. Room and board are provided for long-term volunteers (1 month or more). Help with data compilation and nest-box maintenance and construction may also be needed at other times of the year. This project is an excellent scientific introduction to ornithological fieldwork for students planning to conduct thesis-level research, or who are looking for research projects to work on. Inquiries from potential research collaborators are also welcome. For more information, contact:
Dr. David Hussell
34 Carr Place
Kanata, Ontario, Canada K2K 1K7
Tel: 613-592-0616
Applications for May/June fieldwork should be received no later than 31 March and include a brief résumé and a covering letter, indicating dates available and whether you hold a driver’s license.
For more information on results from the Tree Swallow program at Long Point:
Bradstreet, M.S.W. 1969. Consecutive nesting of female Tree Swallows at Long Point, Ontario. Ontario Bird Banding 5: 68-71.
Holroyd, G.L. 1972. Resource use by four avian species of aerial insect feeders. M.Sc. thesis, Univ. of Toronto.
Holroyd, G.L. 1975. Nest site availability as a factor limiting population size of swallows. Can. Field Nat. 89: 60-64.
Holroyd, G.L. 1983. Resource use by four avian species of aerial insect feeders. Ph.D. thesis, Univ. of Toronto.
De Steven, D. 1978. The influence of age on the breeding biology of the Tree Swallow, Iridoprocne bicolor. Ibis 120: 516-523.
Dunn, E.H. 1979. Age of effective homeothermy in nestling Tree Swallows, Iridoprocne bicolor, according to brood size. Wilson Bull. 91: 455-457.
DeSteven, D. 1980. Clutch size, breeding success, and parental survival in the Tree Swallow. Evolution 34: 278-291
Hussell, D.J.T. 1982. Longevity and fecundity records in the Tree Swallow. N.Am. Bird Bander 7: 154.
Hussell, D.J.T. 1983a. Tree Swallows raise two broods in a season. Wilson Bull. 95: 470-471.
Hussell, D.J.T. 1983b. Age and plumage color in female Tree Swallows. J. Field Ornithol. 54: 312-318.
Quinney, T.E. 1983. The relation between food abundance and reproductive performance of Tree Swallows. Ph.D. thesis, University of Western Ontario.
Quinney, T.E. 1983. Tree Swallows cross a polygyny threshold. Auk 100:750-754.
Quinney, T.E. and C.D. Ankney. 1985. Prey size selection by Tree Swallows. Auk 102: 245-250.
Quinney, T.E. 1986. Male and female parental care in Tree Swallows. Wilson Bull. 98:147-150.
Quinney, T.E., D.J.T.Hussell and C.D. Ankney. 1986. Sources of variation in growth of Tree Swallows. Auk 103: 389-400.
Hussell, D.J.T., and T.E. Quinney. 1987. Food abundance and clutch size of Tree Swallows, Tachycineta bicolor. Ibis 129: 243-258.
Hussell, D.J.T. 1988. Supply and demand in Tree Swallow broods: a model of parent-offspring food-provisioning interactions in birds. Am. Nat. 131: 175-202.
Hussell, D.J.T. 1991. Regulation of food provisioning in broods of altricial birds. Acta XX Congressus Internationalis Ornithologici: 946-960.
Bishop, C.A., M.D. Koster, A. Chek, D.J.T. Hussell, and K. Jock 1995. Chlorinated hydrocarbons and mercury in sediments, Red-winged Blackbirds (Agelaius phoeniceus) and Tree Swallows (Tachycineta bicolor) from wetlands in the Great Lakes – St. Lawrence River Basin. Environmental Toxicology and Chemistry 14: 491-501.
Hussell, D.J.T., and S.J. Anderson. 1999. Longevity record for the
Tree Swallow. North American Bird Bander 24: 6-8.
