Timing of pair formation and male acquisition of alternate plumage by three wintering dabbling ducks

Pair formation in ducks is thought to be influenced by the acquisition of breeding plumage, the occurrence of courtship display, or both. We examined the frequency of pair formation in Mallard (Anas platyrhynchos), Green-winged Teal (Anas crecca carolinensis), and Northern Shoveler (Spatula clypeata) in the central valley of California in relation to the frequencies of male attainment of breeding plumage and courtship display. Predictions related to two hypotheses are: (1) the timing of pair formation is directly related to the attainment of breeding (definitive alternate) plumage by males, and (2) frequencies of courtship display are highest during pair formation. Most female Mallard were paired by the end of October, with >80% in pairs by early December. Of Northern Shoveler, 90% were paired by early January and 90% of female Green-winged Teal were paired by early February. The highest rates of courtship display by Mallard were observed during October through November, by Northern Shoveler in November, and by Green-winged Teal in November through January. Courtship display was, therefore, relatively frequent at the same time as pair formation for all three species. Northern Shoveler spent less time in courtship display than the other two species. Most (90%) male Mallard had acquired alternate plumage by mid-November, Northern Shoveler by early February, and Green-winged Teal by mid-December. Thus, timing of pair formation coincided with timing of attainment of breeding plumage in Mallard and Green-winged Teal but not Northern Shoveler.

Male fairy-wrens produce and maintain vibrant breeding colors irrespective of individual quality

Conspicuous colors may signal individual quality if high-quality individuals produce more elaborate colors or have a greater capacity to invest in color maintenance. We investigate these hypotheses using repeated within-individual observations and experimentally induced color production in a wild bird, the superb fairy-wren (Malurus cyaneus). Male superb fairy-wrens undergo an annual molt from brown, nonbreeding plumage to an ultraviolet-blue and black breeding plumage. Color maintenance is especially relevant for this species because structural, ultraviolet-blue plumage colors are particularly susceptible to fading. Further, only the most sexually attractive males molt to breeding plumage early (before spring) and thereby keep their colors for an extended time before the breeding season. Our results show that (i) sexually attractive, early-molting males do not have higher quality breeding colors and (ii) breeding colors are not impacted by experimentally inducing males to molt early and while in low body condition. We found that (iii) breeding colors do not fade but remain consistent or become more saturated within individuals over time. Despite this, (iv) males do not spend more time preening while in breeding plumage. Instead, males keep their colors in pristine condition by re-molting parts of their breeding plumage throughout the breeding season, suggesting an alternative, potential cost of maintaining ornamental colors. We conclude that variation in structural breeding colors is unlikely to indicate individual quality in superb fairy-wrens.

New record of the Endangered Black-bellied Tern, Sterna acuticauda J.E. Gray 1831, from Tungabhadra River at Siruguppa, Bellary, Karnataka, India

Black-bellied Tern, Sterna acuticauda J.E. Gray, 1831, is an Endangered species currently restricted to a few patches along the major rivers and lakes in the Indian subcontinent. I report it from Tungabhadra River at Siruguppa for the first time. Five individuals in breeding plumage were observed at a 6 km stretch of river, sampled using line transect method. Previous records, with this new locality, suggest that the population of Black-bellied Tern could be fragmented. This new site could be a promising breeding ground for the species; nevertheless, it is under threat owing to uncontrolled sand mining.

No evidence for an adaptive role of early molt into breeding plumage in a female fairy wren

The evolution of ornaments as sexually selected signals is well understood in males, but female ornamentation remains understudied. Fairy wrens offer an excellent model system, given their complex social structure and mating systems, and the diversity of female ornamentation. We investigated whether early molt into ornamental breeding plumage plays an adaptive role in females of the monogamous purple-crowned fairy wren Malurus coronatus, the only fairy wren known to have female seasonal plumage. Using 6 years of monitoring, we found that the timing of female molt was similar to males, but there was no evidence for assortative mating. Like males (previous study), older and dominant individuals acquired their breeding plumage earlier; however, in contrast to males, early molt did not seem to be costly since unfavorable environmental conditions or previous reproductive effort did not delay molt. Early female molt was not associated with any indicator of reproductive quality nor did it attract additional offspring care by their partners. We also found no association between early molt and the likelihood of acquiring a dominant (breeding) position or with the presence or proximity to same-sex rivals. Our study results, which are similar to previous findings in conspecific males, suggest that directional selection for early molt might be relaxed in this species, in contrast to other genetically polygamous fairy wrens in which early molt predicts extrapair mating success in males. However, the finding that molt timing is status dependent raises the possibility that other attributes of the ornament may fulfill an adaptive function in females.

Character displacement within the breeding area questions reinforcement in Ficedula flycatchers

At present, studies of reinforcement should be focused on demonstrating how often this process occurs in nature and how important it is for speciation. Here we study the character displacement within the breeding area in the Pied Flycatcher to check the validity of the reinforcement in Ficedula flycatchers. We used point-referenced spatial data and a random forest to find the most important explanatory factors of the character displacement, and to reconstruct the phenotypic structure of the populations. The environmental temperature, and not the distance to sympatry, were proven to better describe the geographic pattern of the mean breeding plumage colour of the Pied Flycatcher populations. We conclude that ecologically distinct adaptations drive the morphological differentiation of the Old World flycatchers, and not reinforcement.

A global analysis of bird plumage patterns reveals no association between habitat and camouflage

Evidence suggests that animal patterns (motifs) function in camouflage. Irregular mottled patterns can facilitate concealment when stationary in cluttered habitats, whereas regular patterns typically prevent capture during movement in open habitats. Bird plumage patterns have predominantly converged on just four types—mottled (irregular), scales, bars and spots (regular)—and habitat could be driving convergent evolution in avian patterning. Based on sensory ecology, we therefore predict that irregular patterns would be associated with visually noisy closed habitats and that regular patterns would be associated with open habitats. Regular patterns have also been shown to function in communication for sexually competing males to stand-out and attract females, so we predict that male breeding plumage patterns evolved in both open and closed habitats. Here, taking phylogenetic relatedness into account, we investigate ecological selection for bird plumage patterns across the class Aves. We surveyed plumage patterns in 80% of all avian species worldwide. Of these, 2,756 bird species have regular and irregular plumage patterns as well as habitat information. In this subset, we tested whether adult breeding/non-breeding plumages in each sex, and juvenile plumages, were associated with the habitat types found within the species’ geographical distributions. We found no evidence for an association between habitat and plumage patterns across the world’s birds and little phylogenetic signal. We also found that species with regular and irregular plumage patterns were distributed randomly across the world’s eco-regions without being affected by habitat type. These results indicate that at the global spatial and taxonomic scale, habitat does not predict convergent evolution in bird plumage patterns, contrary to the camouflage hypothesis.