Mating systems, parasites and plumage dimorphism in waterfowl

Abstract

Despite a tendency for males of polygynous bird species to show bright or elaborate plumage, comparative analyses have failed to show any consistent relationship between male brightness or plumage dimorphism and the form of breeding systems. Here we argue that this may be partly because the opportunity for sexual selection varies between species showing serial or seasonal monogamy and life-long monogamy. In waterfowl, both the brightness of male plumage and sexual dimorphism in colouration vary between these categories of monogamy. Other ecological factors related to male brightness or plumage dimorphism include male assistance in protecting young, latitude and an index of parasite sharing. The adaptive significance of these trends is discussed.

Comparative reproductive success of communally breeding burying beetles as assessed by PCR with randomly amplified polymorphic DNA.

“…However, the duration of care of the first male to depart was positively correlated with the proportion of his offspring (r = 0.77, n = 10, P = 0.01). (13,14). More than two beetles may be more successful in competition with larger congenerics (ref.…”

“…Larval development is complete 7-8 days later. Both parents perform the same broodcare behavior while maintaining the carcass and provisioning the larvae (12), but the principal benefit of male assistance is to help protect the brood from infanticide by conspecific intruders (13,14). Male Nicrophorus orbicollis usually remain until a few days after eggs hatch, when the carcass is partially consumed and less valuable to competitors; females remain until larval development is complete (6).…”

Migration and the evolution of sexual dichromatism: evolutionary loss of female coloration with migration among wood-warblers

“…This latitudinal gradient has been noted broadly across North American passerines [19] and waterfowl [21], and specifically across New World orioles and wood-warblers [22]; however, only the waterfowl study was analysed in a phylogenetic context. Although this geographical gradient has been widely recorded, little comparative research has tested how changes in female phenotype contribute to this pattern (but see [5,8,14]).…”

A comparative study of egg mass and clutch size in the Anseriformes

“…10°S and 10°N are equivalent); (6) migration distance, calculated as the number of degrees between breeding and wintering latitudes (the latter calculated in the same way as the former); (7) breeding range, estimated as the number of squares occupied during the breeding season in the WORLDMAP grid, a projection of the world divided in equal-area grid squares of ca. 611,000 km 2 (Gaston and Blackburn 1996;Williams 1996);(8) hemisphere, a categorical variable indicating in which hemisphere (North or South) most of the breeding area of the species occurs; (9) migratory behaviour, a categorical variable for migratory and sedentary species, classifying a species as migratory when distance between mean breeding and wintering latitudes exceeds one degree of latitude; (10) nest placement, a categorical variable indicating whether or not the species nests mainly in cavities; (11) mating system, a categorical variable for species pairing less than, or at least, once a year (after Scott and Clutton-Brock 1989); (12) sexual dichromatism, scoring species as sexually dimorphic in coloration or not, based on the colour plates of Madge and Burn (Madge and Burn 1988); (13) insularity, a categorical variable with species endemic to islands with an area of less than 20,000 km 2 , and those with a wider distribution (after Green 1996). Body mass, egg and clutch mass and breeding range were log transformed previous to analyses.…”