Effects of breeding density, synchrony, and experience on extrapair paternity in tree swallows

AbstractIn many birds, populations breeding at higher latitudes have larger clutch sizes. It has been hypothesized that this relationship results from the greater availability of food at higher latitudes. We examined geographic variation in clutch size of Tree Swallows (Tachycineta bicolor) in relation to latitude, longitude, laying date, breeding density, elevation, and summer actual evapotranspiration (AE). AE is a measure of terrestrial primary productivity, and we assumed that it was correlated with resource abundance. Clutch size data were compiled from nest records throughout the breeding range in the United States and Canada (n = 7,459). Summer AE estimates were made from long-term climatological records, and breeding density was estimated from Breeding Bird Surveys. All variables were averaged for each 1° block of latitude and longitude (n = 85 latilong blocks). We found a strong positive relationship between clutch size and latitude. Absolute levels of resource abundance (summer AE) were not related to clutch size but were related inversely to latitude and longitude. After controlling for the effects of confounding variables, clutch size was related positively to latitude and relative resource abundance (summer AE after controlling for breeding density). Our results are consistent with Ashmole's hypothesis that relative, rather than absolute, levels of resource abundance determine at least some of the variation in clutch size.

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Extrapair paternity and variance in reproductive success related to breeding density in Bullock's orioles

Animal Behaviour ◽

10.1006/anbe.2001.1778 ◽

2001 ◽

Vol 62 (3) ◽

pp. 519-525 ◽

Cited By ~ 53

Author(s):

David S. Richardson ◽

Terry Burke

Keyword(s):

Reproductive Success ◽

Breeding Density ◽

Extrapair Paternity ◽

Variance In Reproductive Success

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Extrapair paternity and egg hatchability in tree swallows: evidence for the genetic compatibility hypothesis?

Behavioral Ecology ◽

10.1093/beheco/10.3.304 ◽

1999 ◽

Vol 10 (3) ◽

pp. 304-311 ◽

Cited By ~ 142

Author(s):

B. Kempenaers

Keyword(s):

Tree Swallows ◽

Genetic Compatibility ◽

Extrapair Paternity ◽

Egg Hatchability ◽

Compatibility Hypothesis

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No Evidence for Effects of Breeding Density and Male Removal on Extrapair Paternity in the Pied Flycatcher

The Auk ◽

10.1093/auk/118.1.147 ◽

2001 ◽

Vol 118 (1) ◽

pp. 147-155 ◽

Cited By ~ 5

Author(s):

Osmo Rätti ◽

Arne Lundberg ◽

Håkan Tegelström ◽

Rauno V. Alatalo

Keyword(s):

Social Relationships ◽

Bird Species ◽

Ecological Factors ◽

Egg Laying ◽

Pied Flycatcher ◽

Breeding Density ◽

Fertile Period ◽

Extrapair Paternity ◽

Mating Patterns ◽

The Cost

Abstract Molecular methods have brought new insight to the study of mating patterns. Extrapair fertilizations (EPF) have proven to be widespread among bird species irrespective of social relationships. Ecological factors, such as breeding density and synchrony, have been suggested as contributors to variation in EPF rates. Absence of a male during the female fertile period may also increase the probability of EPFs. In this study, we examined experimentally whether breeding density and male absence before egg-laying influence the EPF rate in Pied Flycatchers (Ficedula hypoleuca). DNA fingerprinting revealed that 4.4% (10/225) of nestlings were the result of EPFs and 7.0% (3/43) of broods included at least one offspring sired by a male other than that attending the nest. We did not find any evidence of higher EPF rate with higher breeding density as stated by the density hypothesis. Contrary to expectation, EPFs were more frequent, though not quite statistically significantly, at low breeding density: all three EPF nests were found in low-breeding-density areas. There was no evidence that EPF rate was affected by a 4 h male removal. In all cases of EPF, an old female was mated with a yearling male, which suggests that older females mated with browner yearling males may have adjusted their initial mate choice through EPCs to acquire indirect genetic benefits. Pied Flycatcher females may be constrained to accept a mate of lower than preferred quality, especially at low breeding density, due to the cost of searching for alternative males.

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Reproductive Anatomy and Indices of Quality in Male Tree Swallows: The Potential Reproductive Role of Floaters

The Auk ◽

10.1093/auk/117.1.74 ◽

2000 ◽

Vol 117 (1) ◽

pp. 74-81 ◽

Cited By ~ 2

Author(s):

Katharina Peer ◽

Raleigh J. Robertson ◽

Bart Kempenaers

Keyword(s):

Sperm Competition ◽

Reproductive Organs ◽

General Assumption ◽

Tree Swallows ◽

Sperm Production ◽

Extrapair Paternity ◽

Competition Theory ◽

Male Tree ◽

Testes Size

Abstract Avian populations often consist of breeding residents and nonbreeding floaters. It is usually assumed that floaters are lower-quality individuals that do not reproduce, but floater tactics and potential reproductive success have rarely been examined carefully. To assess the potential reproductive role of male floaters in Tree Swallows (Tachycineta bicolor), we compared their reproductive organs and morphology with those of resident males. Tree Swallows show high levels of extrapair paternity, but two studies attempting to find the fathers of the extrapair offspring have been remarkably unsuccessful. Floater males that father extrapair young would face intense sperm competition. Theory predicts that under intense sperm competition, selection favors males that produce more sperm. Comparative studies in birds and other taxa provide evidence that the level of sperm competition influences relative testes size and sperm production. However, intraspecific adaptations to different levels of sperm competition have received far less attention. Floater Tree Swallows did not differ from resident males in any of the characters we measured, including testes size, but floaters had significantly larger cloacal protuberances. Thus, our results do not confirm the general assumption that floaters are lower-quality individuals that do not reproduce. Furthermore, floaters showed high variation in the volume of the cloacal protuberance (reflecting sperm numbers), which suggests that they engage in copulations. We conclude that floater male Tree Swallows invest heavily in sperm production (as do resident males) to exploit breeding opportunities through takeovers or extrapair copulations.

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