Study of vocalizations of Herpsilochmus antwrens in northeastern Brazil revealed that the traditional H. pileatus complex is comprised of not two but three species-level taxa. We show that the systematics and biogeography of the group have been based on an unnamed species that has been called H. pileatus for most of this century. Here, we name this “new” species and conclude that its several morphological and vocal distinctions clearly set it apart from other members of the complex. True H. pileatus, as determined through comparison of the lectotype with recently collected specimens and from the distribution of recordings, is confined to southern coastal Bahia. Morphological and vocal analyses suggest that H. pileatus and H. atricapillus are each other's closest relatives. We provide a simple key to diagnostic plumage and mensural characters to permit identification of museum specimens. An extensive series of specimens demonstrated that H. atricapillus includes two male morphs. Geographic overlap of pure morphs in southern Goiás, and the existence of some apparent intermediates in this general area, suggest secondary contact of two weakly differentiated populations, perhaps along complex habitat gradients. Analysis of recordings of H. atricapillus disaggregated geographically and by male morph revealed no diagnostic (by criteria of Isler et al. [1998]) variation within that species, although average measures of overall pace and pace of three sections of loudsongs differed between the morphs by approximately 20%, which we interpret as another indication of incipient differentiation. Revision of the Herpsilochmus pileatus complex provides a case in point for the fundamental role in conservation of both field and taxonomic research and demonstrates the importance of examination of type specimens and inclusion of topotypical samples (whether anatomical, biochemical, or tape recordings) in studies of taxonomy and systematics.

We tested Field Sparrows (Spizella pusilla), Vesper Sparrows (Pooecetes gramineus), Lark Sparrows (Chondestes grammacus), Grasshopper Sparrows (Ammodramus savannarum), Dickcissels (Spiza americana), Eastern Meadowlarks (Sturnella magna), and Western Meadowlarks (S. neglecta) to determine whether the low level (<10%) of observed parasitism by Brown-headed Cowbirds (Molothrus ater) on these grassland hosts is a result of egg rejection. Western Meadowlarks rejected 78% of artificial and real cowbird eggs, Eastern Meadowlarks rejected 36% of artificial cowbird eggs, and Dickcissels rejected 11% of artificial cowbird eggs. None of the other hosts regularly rejected cowbird eggs. Thus, egg rejection may account for some, but not all, of the low level of observed parasitism on grassland hosts in the Midwest. Meadowlarks were also tested with nonmimetic eggs, and the remaining hosts were tested with undersized mimetic and nonmimetic eggs when possible. All hosts, with the exception of the Field Sparrow, demonstrated some level of rejection of the nonmimetic eggs. These results suggest that some grassland hosts, which apparently have been in contact with cowbirds the longest, have evolved some form of rejection behavior that might have selected for mimetic eggs in cowbirds. The intermediate levels of rejection by both species of meadowlarks also may indicate that rejection is increasing in these populations.

We manipulated brood sizes of Tree Swallows (Tachycineta bicolor) in 1996 and 1997 to test for the existence of intra- and intergenerational costs of reproduction. Modal clutch size was six eggs, but experimental brood sizes ranged from two to nine young. Nestling starvation was higher in 1996 (and dependent on brood size) than in 1997, but in both years enlargement of brood size resulted in increased productivity. Nestling mass near fledging was negatively correlated with brood size, but tarsus length and wing chord were not. Food deliveries by parents increased steadily between broods of two to six young but then remained constant between broods of six to nine young. The loss of female mass between incubation and the end of the nestling period was positively related to the pair's total feeding effort, and female mass near fledging declined with increasing brood size. The latter decline disappeared, however, when broods of nine were omitted. Adult return rate (1996 to 1997) was highest among birds that raised enlarged broods. Our results, and a review of other studies of Tree Swallows, suggest that broods of seven or eight young can be raised without costs to the parents or young, and it appears that costs associated with feeding young have not influenced annual fecundity of Tree Swallows. Rather, egg production is most likely limited by energy availability to laying females. A major cost of reproduction for Tree Swallows probably arises from nest-site competition in that early arrival in spring to obtain nest sites exposes adults to high risks of death from starvation.

We investigated the effects of clearcut stand size on species richness, reproductive effort, and relative abundance of scrub-successional birds and the entire bird assemblage at the Savannah River Site in South Carolina. We used standardized mist-net grids to mark and recapture birds in clearcuts replanted with longleaf pine (Pinus palustris) in stands of 2 to 57 ha that were two to six years old. Species richness for the entire bird assemblage was not explained by stand size (P = 0.67), stand age (P = 0.95), or the interaction of these two variables (P = 0.90). Similarly, species richness of scrub-successional birds was not explained by stand size (P = 0.63), stand age (P = 0.55), or the interaction of stand size and stand age (P = 0.35). Regressing species richness on clearcut stand size, we found a significant negative relationship between these variables for the entire bird assemblage (P = 0.01) and for scrub-successional birds (P = 0.02). The ratio of juveniles to adults in mist-net samples varied by year (P = 0.04), but neither clearcut size (P = 0.23) nor the interaction of clearcut size and year (P = 0.25) was related to the ratio of juveniles to adults in the sample. We found no relationship between the frequency of capture of any category of birds and stand size (scrub-successional, P = 0.52; woodland, P = 0.77; combined sample, P = 0.55). Neither bird-species richness, reproductive effort, nor relative abundance differed across clearcut stand sizes. Clearcut stand size does not appear to be an important management variable if variation in species richness, reproductive effort, or relative abundance are objectives. We suggest that even-aged forestry is a useful tool for managing birds in the southeastern United States.

Numbers of Bell's Vireos (Vireo bellii) have declined throughout much of the breeding range in recent years, yet little information exists to determine factors that are causing these declines. We studied Bell's Vireos nesting in grassland-shrub habitats at two study areas in central Missouri to determine reproductive performance, survival, and population growth potential. Birds were color banded and observed during the breeding seasons of 1996, 1997, and 1998 to determine seasonal fecundity. We monitored 124 breeding pairs (127 pair years) and 213 nests. Density declined from 1.00 to 0.80 territories per 10 ha at the first site and increased from 1.11 to 1.33 at the second site during the study. Mean nesting success was 31 ± SE of 0.03% overall and ranged from 13 to 42% among years and study areas; 57% of the pairs fledged at least one young. Low annual production was a function of high rates of nest predation (41% of all nests observed, accounting for 44 to 78% of daily nest mortality annually) and nest parasitism by Brown-headed Cowbirds (Molothrus ater; 29% of nests observed, 17 to 37% of daily nest mortality annually). Mean seasonal fecundity was 1.60 young fledged per pair per year (range 1.00 to 1.79). Annual survival of adults was 61 ± 0.04% and was higher than previously reported. We used our estimates of seasonal fecundity and annual survival of adults to determine the finite rate of increase (λ) for our study population. Our study areas seemingly comprised sink habitats (λ = 0.85). Thus, the vireos on our study areas likely were limited by low reproductive success. Population declines also may be caused by habitat loss, which highlights the need for investigation of historical and current rates of loss of grassland-shrub habitat.

We asked whether geographic variation exists in the complexity of song repertoires in Song Sparrows (Melospiza melodia) by quantitatively comparing four measures of repertoire organization across four geographically distant populations: (1) repertoire size (the number of distinct song types), (2) the number of “minimal units of production” per repertoire, (3) mean similarity among variants of the same song type (“within-type” similarity), and (4) mean similarity among song types in a repertoire (“between-type” similarity). We found significant geographic differences among populations in three of these four measures, with mean similarity among song types being the exception. In general, relatively sedentary populations in North Carolina and Washington were more similar to each other than to migratory populations in Pennsylvania and Maine. Contrary to our expectation based on prior interspecific analyses of variation in repertoire complexity, the relatively sedentary populations in our sample had more complex repertoires than did the more migratory populations. The origin and functional significance of population differences in repertoire complexity in this species remain uncertain.

Brood-parasitic nestlings have a unique opportunity to encounter host-specific lice (Phthiraptera). Lice are permanent ectoparasites found strictly on the body of the host, and they are transferred almost exclusively by bodily contact during copulation and care of young. We investigated whether Brown-headed Cowbird (Molothrus ater) nestlings become infested with lice from their host parents and carry these after fledging, in effect bearing ectoparasite indicators of the species that raised them. Examining lice on cowbirds to identify foster parents would be less costly than determining parasitism patterns in the conventional way by finding many host nests. The 244 cowbird fledglings that we examined carried 11 species and 6 genera of lice, almost the entire spectrum of louse genera known from passerines. We also examined 320 songbirds from 30 species of hosts. As a group, the diversity of louse species on hosts was comparable to that on fledgling cowbirds: 13 species and 7 genera. In contrast, most individual host species yielded only one or two louse species, significantly fewer than on cowbird fledglings. Of 44 fledgling cowbirds with lice, 11 were linked with probable avian foster parents, and 18 other fledglings were linked with one of two possible foster parents. We conclude that cowbird fledglings carry away host lice and that our technique provides a partial assessment of parasitism patterns. The incomplete state of louse taxonomy requires that users of the technique obtain a reference collection of lice from host species in addition to the sample collection from cowbird fledglings. Lice from cowbird fledglings can be identified by a taxonomist and linked to particular host species, and the principal difficulty is the scarcity of skilled louse taxonomists. We also found an unusually rich louse fauna on 219 adult cowbirds, which supports the interpretation that lack of opportunity due to physical isolation has been the fundamental factor in the host specificity of lice in certain avian orders.

Carotenoid pigments produce the ornamental red, orange, and yellow integumentary coloration of many species of animals. Among individuals of a population, the hue and saturation of carotenoid-based ornaments can be extremely variable, and studies of fish and birds have shown that females generally prefer males that display the most saturated and reddest coloration. Consequently, there has been a great deal of interest in determining the proximate factors that affect individual expression of carotenoid-based pigmentation. Parasites might affect production of ornamental coloration, and the Hamilton-Zuk hypothesis proposes that parasitized males will show decreased expression of the secondary sexual traits preferred by females. We found that captive male House Finches (Carpodacus mexicanus) experimentally infected with Isospora spp. (coccidians) and/or Mycoplasma gallisepticum produced carotenoid-based plumage coloration that was significantly less red and less saturated than that of noninfected males. These observations validate a necessary condition of the Hamilton-Zuk hypothesis, but heritable resistance to the pathogens we examined remains to be demonstrated.

Tiny hoopoe-like birds of the extinct family Messelirrisoridae are among the predominant small perching birds in the Middle Eocene (ca. 49 million years ago) avifauna of Messel (Hessen, Germany). Members of the Messelirrisoridae are the earliest-known representatives of the hoopoe/wood-hoopoe lineage and are sister taxa of recent Upupidae (hoopoes) and Phoeniculidae (wood-hoopoes). Outgroup comparison with the Messelirrisoridae facilitates character-state analysis within the Phoeniculidae and Upupidae. In this study, I describe a new species, Messelirrisor grandis, which is the largest species of the Messelirrisoridae known so far.

We determined patterns of nutrient-reserve use by female Northern Shovelers (Anas clypeata) nesting at Minto Flats, Alaska, and compared them with those of female shovelers nesting in the Prairie Pothole Region of Manitoba, Canada. Individual variation in somatic lipid was best explained by nest initiation date; females that initiated nests early had larger lipid reserves than females that delayed nest initiation. These results contrast with those from Manitoba, which showed that females used lipid reserves and stored protein during egg production. Incubating females from Alaska did not use protein or mineral reserves, but lipid reserves decreased significantly throughout incubation. Females in Alaska and Manitoba used lipid reserves similarly during incubation. We conclude that endogenous nutrient availability does not proximately limit clutch size during laying for this population of shovelers, possibly due to the high productivity of wetlands in interior Alaska and/or the long photoperiod that allow females to forage extensively. Successful completion of incubation or brood rearing may be an ultimate factor that controls clutch size for this population of shovelers.

We investigated hatchling and fledgling sex ratios in Eurasian Oystercatchers (Haematopus ostralegus) using random amplified polymorphic DNA markers. The overall hatchling (53% males, n = 374 hatchlings from 177 broods) and fledgling (49% males, n = 51) sex ratio did not differ significantly from unity. Hatchling and fledgling sex ratios were not correlated with laying date, clutch size, brood size, egg-laying sequence, territory quality, male age, or male breeding experience, but hatchling sex ratio was positively correlated with age and breeding experience of females (0.05 < P < 0.075, n = 71). Older females produced more sons irrespective of the position of the offspring in the egg-laying sequence. Fledging mass was not correlated with female age, so the Trivers and Willard (1973) hypothesis is unlikely to explain our results. Sons dispersed less than daughters, so the local resource competition hypothesis of Clark (1978) might apply. The adaptive significance of a male-biased sex ratio in clutches produced by older females is speculative because the costs and benefits of dispersing versus philopatric offspring to parents and offspring are largely unknown.

Chemical contaminants in the environment can influence both morphological and behavioral traits. Ornamental traits such as plumage color may be especially valuable in detecting the effects of toxic chemicals in the environment, although they have been little used to date. We examined patterns of plumage color in subadult female Tree Swallows (Tachycineta bicolor) breeding in an area on the Hudson River that had high levels of PCB contamination and compared them with specimens from other parts of the species' range and with data from two previous studies of plumage color. Tree Swallows are one of the few species of birds where females, but not males, have a distinctive subadult plumage during their first breeding season. Females from four breeding colonies in contaminated areas had significantly more adult-type blue-green coloring than females from the rest of the species' range. Subadult female plumage color at these sites formed a continuum between the normal dull brown plumage found elsewhere and the blue-green plumage of older females. Among these subadults, more colorful individuals bred earlier, and earlier breeding in turn led to larger clutches. The patterns of plumage anomalies described here are consistent with disruption of the endocrine system resulting in the early expression of an adult trait. This study supports recent suggestions that examining variation in ornamental traits of animals is an efficient means of detecting effects of chemical contaminants in the environment.

Fledging (i.e. leaving the nest) in altricial birds is a major step toward independence. The timing of this important event may be influenced by nestling development, parental behavior, and sibling interactions. In this study, we examine the effect of these factors on fledging in Tree Swallows (Tachycineta bicolor). Wing length explained a significant proportion of the variance in fledging age across broods. Similarly, within broods, longer-winged nestlings fledged before shorter-winged nestlings. Feeding rate per nestling did not decrease in the period leading up to fledging, as might be expected if parents stimulated fledging by decreasing their feeding rate. Parental activity near the nest varied in that the frequency of parental passes and hovers within 1 m of the nest opening increased in the period before fledging. Brood size also explained a significant proportion of the variance in fledging age independent of wing length, although the direction of the relationship was not consistent across years. Finally, longer-winged nestlings spent more time in the nest opening and initiated fledging of the brood more often than did shorter-winged nestlings. Overall, our study suggests that nestling development is the most important determinant of fledging age in this species. Once a critical wing length has been reached, sibling interactions, and possibly parental behavior, may influence the timing of fledging.

We sequenced mitochondrial DNA (mtDNA) from cytochrome b (cyt b) and the control region (CR) for all five extant species in the genus Tragopan. We incorporated information on comparative patterns and rates of molecular evolution into phylogenetic analyses, using both a single-gene and a combined data approach. Sequence variability was distributed heterogeneously among the three domains of CR and the three codon positions of cyt b, but the two genes evolved at comparable rates, on average, and produced concordant topologies independent of the method used for phylogenetic reconstructions. Phylogenetic trees suggest that Tragopan includes two main evolutionary lineages grouping caboti-temminckii (clade A), and blythii-satyra (clade B). A shorter CR sequence from one museum sample could not consistently resolve the position of T. melanocephalus. The mtDNA phylogeny is better supported than alternative topologies inferred from morphological and behavioral traits and is compatible with a mechanism of allopatric speciation of Tragopan in two different episodes about 4 and 2 million years ago. In those periods, the vicariant events that might have fostered allopatric speciation of Tragopan are represented by landscape changes that affected the Indohimalayan region after the sudden rising of the Himalayas less then 8 million years ago, and by climatic fluctuations during the Pleistocene less than 2 million years ago.

Red-legged Kittiwakes (Rissa brevirostris) and Black-legged Kittiwakes (R. tridactyla) are morphologically similar, breed in mixed colonies, and nest at the same time, but they exhibit substantial differences in diet, rate of nestling provisioning, and foraging distribution. We cross-fostered nestlings of the two species to test the competing hypotheses that growth in mass of kittiwakes is constrained by diet (i.e. composition, provisioning rate, and quality) or by inherent species-specific physiology. Survival and body mass of cross-fostered nestlings at 30 to 32 days posthatching did not differ from those of conspecific controls. Black-legged Kittiwake fledglings had higher lean mass than Red-legged Kittiwake fledglings regardless of whether they were raised by foster or natural parents. However, nestlings of both species raised by Red-legged Kittiwakes were 50% fatter at 30 to 32 days posthatching than those raised by Black-legged Kittiwakes. Regurgitations from nestlings raised by Red-legged Kittiwakes consisted primarily of lanternfish and contained about twice the lipid (percent dry mass) as regurgitations from nestlings raised by Black-legged Kittiwakes. Consequently, growth rate of lean tissue was genetically and/or physiologically constrained, whereas rate of fat deposition was constrained by diet. We hypothesize that the adaptive significance of lanternfish in diets for Red-legged Kittiwake nestlings is manifest in higher prefledging and/or postfledging survival. Interspecific differences in energy density of food and food provisioning rates balanced each other so that rates of energy provisioning were similar.

The following critiques express the opinions of the individual evaluators regarding the strengths, weaknesses, and value of the books they review. As such, the appraisals are subjective assessments and do not necessarily reflect the opinions of the editors or any official policy of the American Ornithologists' Union.