Christopher W. Thompson

The sequence of molts and plumages in painted buntings and implications for theories of delayed plumage maturation

Within a week of fledging, juvenile Painted Buntings, Passerina ciris, undergo a previously unrecognized first prebasic molt that includes most to all body plumage except greater primary and greater secondary coverts. This molt occurs from early June to early October, usually on the breeding ground. The resulting first basic plumage is similar to juvenal plumage, but is more adult female-like in color in both sexes. First-year, but not adult, Painted Buntings subsequently undergo a presupplemental molt during which the outer four or five primaries, inner four to six secondaries, all remiges, and all body plumage except some to all greater primary coverts typically are replaced. The resulting supplemental plumage is identical in both sexes and is more adult female-like in color than the previous first basic plumage. Presupplemental molt usually occurs between early September and early November. Most (90%) Painted Buntings along the eastern coast ofthe United States undergo this molt on the breeding ground prior to fall migration; whereas, in the western United States, most (60%) molt in exclusively migratory areas of the desert southwestern United States and northwestern Mexico. These desert locations exhibit a large increase in plant and insect life in response to “monsoon” rains that occur predictably in these areas in late summer and fall. Selection may have favored evolution of molt-migration strategies in Painted Buntings in the western United States as a mechanism to allow them to molt in areas with greater food resources than exist at the same time of year on their breeding or wintering ground. Painted Buntings are one of only six passerines in which molt-migration has been documented. All age and sex classes undergo a partial prealtemate molt that was described previously (Fisk 1974) but has been overlooked by all subseauent investigators. This molt usuallv occurs on the wintering ground, and is typically limited to the her& breast, and belly. Most plumage grown by subadult males during first prealtemate molt is adult female-like in color. This is the only passerine known in which sexually mature subadult males grow adult femalelike rather than adult male-like plumage during prealtemate molt. Juvenal plumage has poor structural integrity compared to subsequent plumages. Its structure facilitates heat transfer to the young by brooding females, but is poorly adapted to protecting juveniles from adverse effects of abiotic factors. Therefore, selection may have favored replacement of juvenal plumage with a structurally stronger first basic plumage as soon as possible after fledging. First-year males and females may undergo presupplemental molt to prevent being identified as first-year birds by adult females and being dominated by them (and possibly by adult males as well if adult males do not usually dominate adult females), or to reduce predation on themselves. That no subadult males acquire a winter plumage intermediate in color between that of adult males and adult females in winter is the first empirical support for Rohwer et al.‘s (1980) model which indicates that selection should favor subadult males with plumages that are completely adult female-like or adult male-like more than plumages that are intermediate between adult males and adult females. These results also support the winter female mimicry hypothesis (Brown and Brown 1988), are consistent with the winter I Received 17 October 1990. Final acceptance 3 January 1991.

The potential importance of migratory stopover sites as flight feather molt staging areas: a review for neotropical migrants

The decline of many species of Neotropical migrants has prompted increased research on their ecology on their breeding and wintering grounds. However, studies of their ecology during migration are relatively few. Despite documentation of molt-migration in at least six Neotropical passerine species, this phenomenon has been ignored in current conservation strategies for Neotropical migrants. In this review paper, we suggest that molt studies need to be done as a way to refine and improve conservation plans for Neotropical migrants. We identify three important questions that merit further study: (1) which Neotropical migrant species undergo flight feather molt at migratory-stopover sites; (2) where are molt-migration stopover sites geographically located; and (3) why are these sites preferred as stopover sites during molt? Finding answers to these questions will allow us to protect molt staging areas occupied by Neotropical migrants during migration as many wetland and nearshore oceanic habitats have been protected for molting waterfowl, shorebirds, and seabirds.

Syntopic Occurrence of Multiple Dewlap Color Morphs in Male Tree Lizards, Urosaurus ornatus

We describe a color polymorphism in male tree lizards, Urosaurus ornatus, that may be one of the most complex social badge polymorphisms known. Male tree lizards in central Arizona possess dewlaps that are solid blue, solid yellow or solid orange, or bicolored consisting of a yellow or orange background with a blue central spot that varies continuously in size from a few scales to 55% of the area of the unextended dewlap. The occurrence of this polymorphism varies geographically and microgeographically, from populations that are monomorphic, to those that are dominated by two dewlap morphs, to those where all five morphs are more equally represented. Comparisons of the frequency of the different morph types both within and between years suggests no evidence of differential fitness between the morphs. Comparisons between habitats suggest that morph complexity was highest in the better quality habitat of the two sites we compared.

Population frequencies of alternative male phenotypes in tree lizards: geographic variation and common-garden rearing studies

Abstract Tree lizards (Urosaurus ornatus) vary in throat fan (dewlap) color. Earlier, we described five dewlap types (Orange, Orange-Blue, Yellow, Yellow-Blue, and Blue), and reported that only males had blue in the dewlap and that presence or absence of a discrete blue patch was correlated with male alternative reproductive phenotypes in a central Arizona population. Here, with a modified scheme characterizing two dewlap elements, background color (orange, yellow, blue) and blue patch occurrence, we assessed: (1) sexual, annual, and geographic variation in the frequencies of dewlap elements; (2) simple habitat correlates; and (3) the effects of laboratory rearing regime on dewlap type. Within a population, frequencies of males and females expressing orange or yellow backgrounds did not differ, suggesting that control of background is similar in the sexes. Within several populations, frequencies of the dewlap elements did not differ across years (and probably generations), indicating that phenotype frequencies are relatively stable. Among five populations frequencies of background colors varied, as did frequencies of male types (blue patch present or absent). Dewlap frequencies did not correlate with habitat (boulders or mesquite trees), although few populations were sampled. In male and female offspring reared from eggs to sexual maturity in a common-garden laboratory study, background color frequencies in both sexes and blue patch frequencies in males differed among offspring from different populations. Offspring frequencies matched respective parental population frequencies. Results suggest that among-population variation in frequencies of the two dewlap elements are mediated by differences in genetics, in maternal effects, or both. Thus, differences in male behavior functionally linked to the blue patch also may be controlled by genetic or maternal effects.

OVERLAP IN DIETS AND FORAGING OF COMMON MURRES (URIA AALGE) AND RHINOCEROS AUKLETS (CERORHINCA MONOCERATA) AFTER THE BREEDING SEASON

Abstract Common Murres (Uria aalge; hereafter “murres“) and Rhinoceros Auklets (Cerorhinca monocerata; hereafter “auklets“) breed and forage sympatrically over much of their range. They have similar diets during the breeding season, which suggests that they partition prey during the breeding season by foraging (1) at different locations, (2) at different times of day, (3) at different water depths, (4) on different proportions of the same prey species, or (5) some combination of the four. We examined possible mechanisms of niche partitioning during late summer and fall in Puget Sound, Washington, in 1993-1996. Murres and auklets fed mainly on Pacific herring (Clupea pallasii, occurring in 74.2% and 48.1%, respectively, of gastrointestinal tracts with contents), Pacific sand lance (Ammodytes hexapterus; 45.8% and 62.3%), and salmonid (Oncorhynchus spp.) species (21.9% and 9.7%). Auklets also consumed considerable amounts of threespine stickleback (Gasterosteus aculeatus; 26.6%). Murres and auklets did not differ significantly (1) in their diet (between age classes or sexes of either species, or among years); (2) in mean lengths of Pacific herring (101 and 109 mm, respectively) and Pacific sand lance (82 and 86 mm) they consumed; or (3) in the mean depth (7–8 m) at which they were entangled in gill nets. Dietary diversity was low, with most gastrointestinal tracts containing only one or two prey species in both murres and auklets. Murres were caught and therefore presumably feed more frequently in the afternoon and evening; whereas auklets were entangled more often in early morning. We found differences between murres and auklets in the diel chronology of prey taken, which may partly explain how murres and auklets coexist during the breeding season and months thereafter, prior to auklet emigration from Puget Sound. Chevauchement du Régime Alimentaire et de la Quête Alimentaire chez Uria aalge et Cerorhinca monocerata après la Saison de Reproduction

ECOSYSTEM‐BASED MANAGEMENT OF PREDATOR–PREY RELATIONSHIPS: PISCIVOROUS BIRDS AND SALMONIDS

Predator-prey relationships are often altered as a result of human activities. Where prey are legally protected, conservation action may include lethal predator control. In the Columbia River basin (Pacific Northwest, USA and Canada), piscivorous predators have been implicated in contributing to a lack of recovery of several endangered anadromous salmonids (Oncorhynchus spp.), and lethal and nonlethal control programs have been instituted against both piscine and avian species. To determine the consequences of avian predation, we used a bioenergetics approach to estimate the consumption of salmonid smolts by waterbirds (Common Merganser, California and Ring-billed Gull, Caspian Tern, Double-crested Cormorant) found in the mid-Columbia River from April through August, 2002-2004. We used our model to explore several predator-prey scenarios, including the impact of historical bird abundance, and the effect of preserving vs. removing birds, on smolt abundance. Each year, <1% of the estimated available salmonid smolts (interannual range: 44,830-109,209; 95% CI = 38,000-137,000) were consumed, 85-98% away from dams. Current diet data combined with historical gull abundance at dams suggests that past smolt consumption may have been 1.5-3 times current numbers, depending on the assumed distribution of gulls along the reaches. After the majority (80%) of salmonid smolts have left the study area, birds switch their diet to predominantly juvenile northern pikeminnow (Ptychocheilus oregonensis), which as adults are significant native salmonid predators in the Columbia River. Our models suggest that one consequence of removing birds from the system may be increased pikeminnow abundance, which--even assuming 80% compensatory mortality in juvenile pikeminnow survival--would theoretically result in an annual average savings of just over 180,000 smolts, calculated over a decade. Practically, this suggests that smolt survival could be maximized by deterring birds from the river when smolts are present, allowing bird presence after the diet switch to act as a tool for salmonid-predator control, and conducting adult-pikeminnow control throughout. Our analysis demonstrates that identifying the strength of ecosystem interactions represents a top priority when attempting to manage the abundance of a particular ecosystem constituent, and that the consequences of a single-species view may be counterintuitive, and potentially counterproductive.

Determining homology of molts and plumages to address evolutionary questions: a rejoinder regarding emberizid finches

Determining how molt is integrated into the annual cycle, and understanding what natural selection pressures have favored the diversity of molt strategies in birds are important issues in ornithology and zoology in general. To study these issues, most omithologists historically have used and continue to use many different nomenclatural systems which tie names of molts and plumages (e.g., breeding plumage, summer plumage, adult plumage) to events in the annual cycle, season or age. However, it is circular to study the evolution of molts and plumages in relation to annual cycle events, seasons or age because the definitions of plumages and molts in these systems are defined in terms of these parameters. To study the evolution of molts and plumages it is essential to use a system such as that proposed by Humphrey and Parkes (1959, 1963) to identify homologous molts and plumages that is independent of annual cycle events, seasons and age. This paper discusses how to use correctly the Humphrey-Parkes system and illustrates this by discussing an example of how the Humphrey-Parkes system was applied incorrectly in a series of studies on Passerina buntings. We also document that Phainopeplas, Phainopepla nitens, Yellowbreasted Chats, Icteria virens. Northern Cardinals, Cardinalis cardinalis, and Orange-breasted Buntings, Passerina leclancherii exhibit a previously unknown sequence of molts and plumages that is homologous to that of other recently studied Passerina species, and suggest that this sequence of molts and plumages probably is much more widespread in birds than is currently recognized.

Is the painted bunting actually two species? problems determining species limits between allopatric populations

Painted Buntings, Passerina ciris, breed in two allopatric eastern and western breeding ranges that differ greatly from the breeding ranges of the two currently recognized subspecies (AOU 1957). These two populations differ dramatically in their timing and pattern of molt and migration. All age and sex classes in the western population typically begin fall migration at least two months earlier than their respective age and sex classes in the eastern population. These birds subsequently interrupt their fall migration in exclusively migratory areas in southern Arizona and northwestern Mexico to begin and complete their annual flight feather molt before continuing their fall migration. In contrast, birds in the eastern population usually complete flight feather molt on the breeding grounds before beginning fall migration. Last, the eastern and western populations winter in allopatric ranges; the eastern population winters in southern Florida, the Bahamas, Cuba, Jamaica, and Haiti, and the western population winters in southern Texas, Mexico and Central America. These data strongly indicate that no significant gene flow occurs between these populations, and suggests that they represent valid phylogenetic species. Two subspecies of Painted Buntings, pallidior and ciris, are currently recognized based on previous studies (Mearns 1911, Storer 1951) that documented variation between the eastern and western populations in winglength of adult (in definitive plumage) males and plumage color of adult males and females on the breeding ground. However, this study indicates that the patterns of variation in these characters in males and females within and between populations are inconsistent with the current subspecific geographic limits in this species, and that separating Painted Buntings into subspecies based on these criteria is not warranted.

Regional population monitoring of the marbled murrelet: field and analytical methods.

The marbled murrelet (Brachyramphus marmoratus) ranges from Alaska to California and is listed under the Endangered Species Act as a threatened species in Washington, Oregon, and California. Marbled murrelet recovery depends, in large part, on conservation and restoration of breeding habitat on federally managed lands. A major objective of the Northwest Forest Plan (the Plan) is to conserve and restore nesting habitat that will sustain a viable marbled murrelet population. Under the Plan, monitoring is an essential component and is designed to help managers understand the degree to which the Plan is meeting this objective. This report describes methods used to assess the status and trend of marbled murrelet populations under the Plan.

EFFECTS OF SIZE AND MIGRATORY BEHAVIOR ON THE EVOLUTION OF WING MOLT IN TERNS (STERNAE): A PHYLOGENETIC-COMPARATIVE STUDY

Abstract Approximately 60% of the 45 species of terns (Sternae) have an unusual form of wing molt in which a variable number of inner primaries and outer secondaries are replaced two or three times in a single year—a process that has been called “repeated molt.” Although several hypotheses have been proposed for the maintenance of repeated molt, few data exist regarding potential selective forces that may have favored the evolution of this molt strategy, and there are no explanations for the high degree of interspecific variation in the extent of repeated molt. Preliminary investigations indicated that large terns tended to have less repeated molt than small terns and that the presence of repeated molt appeared to be associated with migratory behavior. We examined these initial findings by combining data from the literature, from examinations of museum specimens, and from a recent molecular phylogeny of the terns to perform phylogenetic-comparative tests. First, we used independent contrasts to verify that the association between large terns and less repeated molt was significant and not a result of shared ancestry. Second, we used tests for binary character association to evaluate the apparent link between repeated molt and migratory behavior. The results of these tests, along with reconstructions of ancestral states, led to a potential explanation for the origin of repeated molt, in which a tropical, sedentary ancestor gave rise to several lineages that spread to temperate areas and adopted a migratory life history. With this shift to a more seasonal regime came shortened breeding periods and perhaps more time for molt, which could have led to modifications of the ancestral molting strategy and the origin of repeated molt. Efectos del Tamaño y del Comportamiento Migratorio en la Evolución de la Muda del Ala en los Gaviotines (Sternae): Un Estudio Filogenético Comparativo