Historical Examination of Delayed Plumage Maturation in the Shorebirds (Aves: Charadriiformes)

Abstract

Delayed plumage maturation refers to the presence of nonadultlike immature plumages (juvenal plumage excluded). It is usually considered the result of selection for distinctive first-winter or first-summer appearance. In the present study, evolution of delayed plumage maturation is examined in the shorebirds: the sandpipers, plovers, gulls, and their allies. Nine plumage-maturation characters were identified, and their states were superimposed onto topologies generated during two recent investigations of shorebird relationships (Sibley and Ahlquist; revised Strauch). The characters were then optimized so as to assign character states to interior nodes of the trees in the most parsimonious way. Reconstructions of character evolution on six of the shortest revised Strauch trees were ambiguous with respect to delayed plumage maturation in the hypothetical ancestral shorebird. If plumage maturation was not delayed in the shorebird ancestor, optimization indicated that delay appeared when nonadultlike juvenal feathers were acquired. In contrast, on the single Sibley and Ahlquist tree, absence of delayed plumage maturation in the shorebird ancestor was indicated unambiguously, with three evolutionary novelties (nonadultlike juvenal feathers, seasonal plumage change, and a reduced first-spring molt) implicated in its acquisition. Optimization indicated that delayed plumage maturation in shorebirds can be explained plausibly without invoking selection for distinctive first-winter or first-summer appearance. Two of the novel conditions generating delayed plumage maturation (modified juvenal feathers and seasonal plumage change) did so only because they were acquired in a taxon possessing restricted first-year molts, which are primitive. Given these observations, it seems simplest to explain the delay in plumage maturation as an incidental consequence of the phylogenetic inertia of shorebird molts. The third novelty that generates delayed plumage maturation, a reduced first-spring molt, may have been acquired to reduce molt-associated energetic demands in young birds.

Enigmatic phylogeny of skuas (Aves: Stercorariidae)

“…If so, this pathway, was ' on ' in the common ancestor of gulls and skuas and remained ' on ' in the Stercorarius lineage, but was set ' off ' in the atharacta lineage and returned to ' on ' in the population that gave rise to the Pomarine skua, S. pomarinus. Comparable lineagespecific changes have been reported in the timing of plumage development characters in other Charadriiform birds (Chu 1994). We cannot realistically speculate about the genetic bases of the behavioural and other morphological similarities between the Pomarine skua and other Stercorarius skuas, S. longicaudus and S. parasiticus, but it is worth noting that neither the Pomarine nor Great skuas are notably deficient in nuclear gene diversity.…”

Contour feather moult of Ruffs Philomachus pugnax during northward migration, with notes on homology of nuptial plumages in scolopacid waders

“…Yet, this species arrives from the West Table 1. Review of the terminology used in the primary and secondary literature to assign the different feather generations carried by adult male Ruffs in the course of the year, together with the suggested terminology based on Humphrey & Parkes' (1959) African wintering grounds \I ith a colourful plumage that partially consists of striped feathers too, and the striped feathers of godmits are \ e n similar in appearance to those of Ruffs (see big 1) The striped feathers presented an enigma to Piersnid and Jukema (1 993) How.=\ er, noting that the feathers that comprise the breast and bellv parts of the breeding plumages of scolopacids \nth more cryptic nuptial plumages, such as man\ shanks and curlews (Tringinae, e g Paulson 1993), are actually quite similar to the striped feathers of Ruffs and Bar-tailed Godit its, we suggest that striped feathers indeed represent the 'original breeding plumage feather type of the sandpiper famih The sho\v\ feathers of the 5upplrmentary plumage thus represent an additional t-eathcr Seneration The existence of 'three different types of summrr-plumage feathers lvas also noted in sex era1 populations of Black-tailed Godwits Limosa iimosa I x Roselaar and Gerritsen (1 99 1) Note that the rtripcd feathers of Golden Plot ers described b, Jukema and Piersma (1987) Chu (1994), seasonal plumage change I \ a den\ ed chard< ter M ithin the Charadriiformes, and i t m a be an CI olutionar) no\el trait ~h i c h may or may m t hale becn shown by the ancestor of the Scolopacidae. Although the monomorphic snipes could represent the ancestral pattern within the Charadriiformes (Chu 1994) (Fig.4A), their plumage monomorphy may also be a derived character (Chu 1994) (Fig.…”

“…Shorebirds, and especially the sandpiper family Scolopacidae, show fascinating variation between species in the extent of the seasonal change in plumage appearance, and a variety of moult strategies to get from one plumage type into another (Cramp & Simmons 1983, Chu 1994, Higgins & Davies 1996, Piersma et al 1996. However, the available descriptions are incomplete and the terminology is confusing (Higgins & Davies 1996: 16-1 7).…”

“…However, the available descriptions are incomplete and the terminology is confusing (Higgins & Davies 1996: 16-1 7). This is an obstacle to the interpretation of the functional significance and evolution of the various moult strategies (Thompson & Leu 1994), an issue that has not been much explored in this group of birds (but see Chu 1994). Although Torresponding author.…”

Understanding Evolution of Plumages and Other Cyclic Avian Life-History Phenomena: Role for an Improved Molt Terminology

“…A comprehensive understanding of the evolution of the highly variable plumages of birds therefore needs consideration of other cyclical aspects of avian life histories (Jacobs and Wingfield 2000), with due attention to the appropriate environmental context. In such an endeavor, the study of plumages seem an obvious place to start, but issues of shared ancestries and homologies provide a real obstacle for progress (Rohwer et al 1992, Thompson and Leu 1994, Chu 1994, Jukema and Piersma 2000. The nomenclatural system designed by Humphrey and Parkes (1959; the H-P system) was ahead of its time and much underused, especially in the Old World.…”