We reviewed the avian literature for quantitative studies of sex biases in dispersal and found continued and strengthened support for the general pattern of female biased dispersal established by Greenwood in 1980. We report sex differences in dispersal patterns in natal and breeding dispersal as measured by 1) proportion leaving and 2) distance moved. Greenwood's review found evidence for male biased dispersal only within four species of the Anatidae. We find there is now evidence for male biased dispersal in twenty-two species representing twelve families.

http://www.jstor.org/stable/pdfplus/3546885.pdf

Sex Biases in Avian Dispersal: A Reappraisal

Informed Dispersal: Prospecting by Birds for Breeding Sites

The hypothesis that patterns of sex-biased dispersal are related to social mating system in mammals and birds has gained widespread acceptance over the past 30 years. However, two major complications have obscured the relationship between these two behaviors: 1) dispersal frequency and dispersal distance, which measure different aspects of the dispersal process, have often been confounded, and 2) the relationship between mating system and sex-biased dispersal in these vertebrate groups has not been examined using modern phylogenetic comparative methods. Here, we present a phylogenetic analysis of the relationship between mating system and sex-biased dispersal in mammals and birds. Results indicate that the evolution of female-biased dispersal in mammals may be more likely on monogamous branches of the phylogeny, and that females may disperse farther than males in socially monogamous mammalian species. However, we found no support for a relationship between social mating system and sex-biased dispersal in birds when the effects of phylogeny are taken into consideration. We caution that although there are larger-scale behavioral differences in mating system and sex-biased dispersal between mammals and birds, mating system and sex-biased dispersal are far from perfectly associated within these taxa.

/pdf/social-mating-system-and-sex-biased-dispersal-in-mammals-and-3a3txypyem.pdf

Social Mating System and Sex-Biased Dispersal in Mammals and Birds: A Phylogenetic Analysis

(1) We compared the laying dates, clutch size, brood size and nestling growth of dippers (Cinclus cinclus) breeding on acidic and circumneutral Welsh streams in 1985 and 1986. Serum calcium and serum alkaline phosphatase concentrations were measured in nestlings and adults from the wild population in 1988-89. (2) Laying dates were later, clutch and brood sizes smaller, and nestling growth slower along acidic streams by comparison with circumneutral streams. All differences were significant. Second clutches were absent from acidic streams, but occurred at 20% of circumneutral sites. (3) Though egg-laying was delayed at higher altitudes, pH had additional significant effects. Pairs began laying later by 13-22 days at acidic sites than circumneutral sites even after removing the effect of altitude. (4) Reduced clutch size at acidic sites in 1986 could be explained solely by delayed laying, but pH had an additional effect in 1985 and in the combined years' data. (5) Smaller broods at acidic sites could be explained solely by reduced clutch size. (6) Reduced daily mass increase in nestlings at acidic sites could be explained by delayed laying, but reduced tarsal growth was affected by pH at P = 006 after accounting for the effects of laying date. (7) Adult mass was significantly lower on acidic streams than on circumneutral streams in the pre-breeding period. The age structure of the population did not differ between the two types of stream, though the sex ratio on acid streams was female biassed. (8) Serum calcium was significantly lower in both males and females at acidic sites in the pre-breeding period than at circumneutral sites. At acidic sites only, females had higher serum calcium than males, and showed also elevated serum alkaline phosphatase. Nestling serum calcium was lower at acidic sites only up to 8 days after hatching. (9) We discuss our results in relation to the reduced availability of calcium in dipper prey along acidified streams.

The ecology of dippers Cinclus cinclus in relation to stream acidity in upland Wales : breeding performance, calcium physiology and nestling growth

We examined 12 825 prey of tree swallows (Tachycineta bicolor) northeast of Sudbury, Ontario, to observe the importance of aquatic food and the influence of wetland pH on swallow diet during the br...

Tree swallow diet in relation to wetland acidity

There is growing concern amongst conservationists about the consequences of ‘acid rain’, though this is not the only way that watercourses can increase in acidity. This study shows that fewer Dippers are present on acidic reaches of rivers, probably because changed water quality affects the birds' food supply.

Is the breeding distribution of Dippers influenced by stream acidity

Between 1978 and 1986, 2500 nestlings and 700 fledged Dippers were ringed on rivers in mid and south Wales. Adults showed strong fidelity to breeding sites, only 3.6% (of 138) moving more than 2.5 km between breeding attempts. By contrast, 30% (of 166) of birds ringed as nestlings moved more than 5 km and up to 32 km from natal sites; post-natal dispersal involved significantly greater distances in females than males, with females significantly more likely to cross watersheds. Dispersal distance showed no correlation with time of fledging in either sex. Actual distances of post-natal dispersal in both sexes were greater than those expected from juveniles replacing likely adult mortality. We discuss our findings in relation to general hypotheses on breeding systems and dispersal patterns.

The post-natal and breeding dispersal of Welsh Dippers Cinclus cinclus

Biometric data were collected from over 500 Dippers in mid and south Wales between 1978 and 1985 Mean wing lengths for both sexes were significantly shorter in first years than in older birds For combined ages, males and females could be separated above and below wing length 92–94 mm; the sex ratio did not differ from 1:1 Wing lengths in both sexes were shorter than in Scandinavian Dippers, although Welsh males had significantly longer wings than males in south west Scotland Body weights in both sexes increased during moult and prior to breeding, and a ‘condition factor'is suggested from regression of weight on wing length Weights of nestlings indicated sex‐related differences, although it was impossible to sex every nestling using weight alone

https://www.tandfonline.com/doi/pdf/10.1080/03078698.1986.9673882

J. M. S. Lewis

Papers

Is the breeding distribution of Dippers influenced by stream acidity

The post-natal and breeding dispersal of Welsh Dippers Cinclus cinclus

Biometrics, growth and sex ratios amongst Welsh Dippers Cinclus cinclus