Humans profoundly affect wildlife through environmental modification but they can also influence wildlife through direct interactions. We surveyed human attitudes and actions towards birds in two urban areas (Seattle, Washington, and Berlin, Germany) to determine whether encouraging (e.g., providing bird feeders) and discouraging (e.g., actively repelling) behavior directed at birds affected bird behavior. We studied human and bird behavior across an urbanization gradient (heavy to light urbanization) in both cities to capture variation in urban cover, human density, attitudes, and actions as well as variation in human culture and socioeconomic condition and education. We found that residents of Berlin encouraged birds more than residents of Seattle did, and that Seattleites discouraged birds more than Berliners. These differences varied across the urbanization gradient. Likewise, birds (crows and other songbirds) varied their flight initiation distance across the urbanization gradient, with distances increasing from urban to rural sites. However, in rural sites in Seattle, American Crows (Corvus brachyrhynchos) and European Starlings (Sturnus vulgaris) had exaggerated flight initiation distances compared with those of American Robins (Turdus migratorius) in Seattle and those of Hooded Crows (C. cornix), House Sparrows (Passer domesticus), and European Starlings in rural Berlin. This exaggerated wariness of humans in crows and starlings is correlated with the relatively high levels of discouraging behavior toward birds by humans in these rural areas in Seattle. These results demonstrate that in addition to habituation to human disturbance, human behavior directed at birds can affect certain species' behavior.

Egg discrimination underlies the evolution of a host's ability to reject a brood parasite's egg, but some hosts do not reject if it is too costly or if the parasitic egg mimics the host egg. We examined cues used by the Yellow Warbler (Setophaga petechia), a host of the Brown-headed Cowbird (Molothrus ater), in its decision to reject (bury or desert) experimentally parasitized clutches. Yellow Warblers that returned to nests after a model egg was added spent significantly more time peering at and probing their nest contents and shuffling than before eggs were added. Rejection probability increased with the proportion of time Yellow Warblers probed their nest contents after settling on their clutch. Accepters and rejecters, however, peered at or shuffled their eggs the same amount of time and visited the nest and probed its contents (before settling) the same number of times. Burial occurred at 29 of 144 nests (20.1%) experimentally parasitized with model cowbird eggs, of which 14 nests survived long enough for replacement clutches to be parasitized. Only one of the 14 (7.1%) females that initially buried parasitized clutches buried again when the replacement clutch was parasitized, whereas the others accepted their parasitized replacement clutch. Repeated parasitism revealed that an individual's response to parasitic eggs is plastic and that it may reject or forgo rejection after recognizing a parasitism event.

Many birds lay eggs speckled with black or reddish-brown spots of protoporphyrin pigment, but the function of these spots is debated. Two recent hypotheses have received considerable attention. Under the “signaling-function hypothesis,” speckling reflects female quality and influences allocation of male parental care; under the “structural-function hypothesis,” the speckles strengthen the eggshell when calcium is scarce. The evidence for each is taxonomically uneven. For instance, evidence for the signaling-function hypothesis comes from cavity-nesting and uniparentally incubating species in which the viewing conditions and possibilities for males to assess the speckling are limited, and male response to speckling is indirect (i.e., female-feeding) or postponed (i.e., chickfeeding). We tested the predictions of both hypotheses in a biparentally incubating ground-nesting shorebird, the Northern Lapwing (Vanellus vanellus), in which the potential for a direct male response to eggshell speckling exists and visual inspection of the eggs is not hindered by light availability in a nest cavity. The speckling parameters (spot intensity, distribution, and cover) were repeatable within Northern Lapwing clutches, a requirement for a sexually selected signal, but we found no relationship between male incubation and speckling. However, the spots were associated with thinner areas of eggshell, which strongly supports the suggestion of a structural (strengthening) function. Our results do not support the signaling-function hypothesis of eggshell speckling, but extend the structural-function hypothesis and prior findings (that speckling occurs primarily at thinner areas of the shell) to other avian taxa. Furthermore, if the generally accepted view that Northern Lapwing eggs are cryptically marked is correct, our findings suggest that more than one significant function can drive the evolution of avian eggshell pigmentation.

Birds that remove ectoparasites and other food material from their hosts are iconic illustrations of mutualistic—commensalistic cleaning associations. To assess the complex pattern of food resource use embedded in cleaning interactions of an assemblage of birds and their herbivorous mammal hosts in open habitats in Brazil, we used a network approach that characterized their patterns of association. Cleaning interactions showed a distinctly nested pattern, related to the number of interactions of cleaners and hosts and to the range of food types that each host species provided. Hosts that provided a wide range of food types (flies, ticks, tissue and blood, and organic debris) were attended by more species of cleaners and formed the core of the web. On the other hand, core cleaner species did not exploit the full range of available food resources, but used a variety of host species to exploit these resources instead. The structure that we found indicates that cleaners rely on cleaning interactions to obtain food types that would not be available otherwise (e.g., blood-engorged ticks or horseflies, wounded tissue). Additionally, a nested organization for the cleaner bird—mammalian herbivore association means that both generalist and selective species take part in the interactions and that partners of selective species form an ordered subset of the partners of generalist species. The availability of predictable protein-rich food sources for birds provided by cleaning interactions may lead to an evolutionary pathway favoring their increased use by birds that forage opportunistically.

Population genetic structure was characterized in Xantus's Murrelet (Synthliboramphus hypoleucus) by analyzing variation in the mitochondrial control region (505 samples) and 12 microsatellite loci (428 samples) in birds captured at all 13 current breeding areas in southern California and northwestern Baja California, Mexico. The two types of molecular markers were consistent in revealing strong genetic differentiation between the two currently recognized subspecies (S. h. hypoleucus and S. h. scrippsi) and little or no differentiation among breeding areas within subspecies. Estimates of gene flow were essentially zero, and no evidence for admixture was found. Gene flow among breeding locations within subspecies, on the other hand, was seemingly high. Given these genetic results, as well as clear morphological differences between the subspecies and the apparent lack of interbreeding at breeding areas where the two forms are sympatric, we suggest that two species be recognized. Both forms are genetically distinct from Craveri's Murrelet (S. craveri), a closely related species whose breeding range partially overlaps that of Xantus's Murrelet. Taxonomic subdivision of Xantus's Murrelet introduces new conservation concerns, especially for S. h. hypoleucus, which urgently requires greater study and protective efforts.

The living and extinct flightless rails of the Pacific are among the most species-rich examples of parallel evolution in vertebrates. The “typical” rails of this region comprise a diverse assemblage of long-billed species variously placed in the genera Rallus, Lewinia, Nesoclopeus, Gallirallus, Habropteryx, Tricholimnas, Aramidopsis, Amaurornis, Eulabeornis, and Habroptila. I present a phylogenetic hypothesis for this group based on Bayesian and maximum likelihood analyses of 12S, control region, and cytochrome-b data obtained from museum specimens (frozen tissues, toe pads from study skins, and bones from archaeological sites) of living and extinct species. All previously recognized genera are either monotypic or non-monophyletic, and I advocate lumping nearly all species into a broadly defined Gallirallus sensu lato. Volant species are not paraphyletic with respect to nearly all flightless species. Instead flightless species branch off in rapid succession from lineages leading to extant volant species. The nesting of the flightless species G. pendiculentus with G. philippensis suggests that the flightless condition may evolve prior to reproductive isolation. A locally calibrated relaxed molecular clock indicates that species from Oceania evolved only within the last 400,000 years, supporting the hypothesis that speciation proceeds rapidly in flightless rails. These results help resolve a long-standing taxonomic quagmire and have important implications for Pacific biogeography and the tempo and mode of speciation in island birds.

The introduction of the Great-tailed Grackle (Quiscalus mexicanus) into the Valley of Mexico by Aztec Emperor Auitzotl (1486–1502) is the earliest documented case of human-mediated bird introduction in the Western Hemisphere. I investigated the origin of the account of this ancient translocation and the team that collected it: Bernardino de Sahagun's research group of elite native scholars from the Royal College of the Holy Cross, Tlatelolco. These scholars, the top academic research group in 16th-century Mexico, used expert native consultants as sources of information and an early form of peer review to detect errors and omissions. The account first appears in extant drafts written by the research group during its field work in Tlatelolco (1561–1565), 59–79 years after Auitzotl introduced the grackles. The account then successfully passed through peer review in Tenochtitlan before being added to the Florentine Codex. The research group was composed of graduates, professors, and an administrator of the Royal College. Professor Antonio Valeriano, a key member of the research group, was married to Isabel Huanitzin, an Aztec princess closely related to Auitzotl. Because all the many details of the account successfully passed peer review, and also because the account lacks the usual warning phrases used to alert the reader to doubtful information such as fables, it is clear that the research group judged the story of Auitzotl's introduction of the Great-tailed Grackle to be true. The presence of an actual conversation in the Aztec text suggests eyewitness testimony or reliance on an earlier-written native manuscript.

Wildlife monitoring surveys are prone to nondetection errors and false positives. To determine factors that affect the incidence of these errors, we built an Internet-based survey that simulated avian point counts, and measured error rates among volunteer observers. Using similar-sounding vocalizations from paired rare and common bird species, we measured the effects of species rarity and observer skill, and the influence of a reward system that explicitly encouraged the detection of rare species. Higher self-reported skill levels and common species independently predicted fewer nondetections (probability range: 0.11 [experts, common species] to 0.54 [moderates, rare species]). Overall proportions of detections that were false positives increased significantly as skill level declined (range: 0.06 [experts, common species] to 0.22 [moderates, rare species]). Moderately skilled observers were significantly more likely to report false-positive records of common species than of rare species, whereas experts were significantly more likely to report false-positives of rare species than of common species. The reward for correctly detecting rare species did not significantly affect these patterns. Because false positives can also result from observers overestimating their own abilities (“overconfidence”), we lastly tested whether observers' beliefs that they had recorded error-free data (“confidence”) tended to be incorrect (“overconfident”), and whether this pattern varied with skill. Observer confidence increased significantly with observer skill, whereas overconfidence was uniformly high (overall mean proportion = 0.73). Our results emphasize the value of controlling for observer skill in data collection and modeling and do not support the use of opinion-based (i.e., subjective) indications of observer confidence.

We describe a stem group representative of Diomedeidae from the early Oligocene (Rupelian) of Belgium. The fossil remains, wing, and pectoral girdle bones of two individuals are described as Tydea septentrionalis, gen. et sp. nov., and constitute the earliest well-established record of the taxon and the first Paleogene record from the North Sea Basin. The new species was about the size of the extant Black-browed Albatross (Thalassarche melanophris) and establishes that albatrosses had already reached a large size 30 mya. The wing bones of T. septentrionalis are distinguished by several plesiomorphic features from those of species in crown group Diomedeidae, which may indicate differences in aerodynamic performance between the fossil species and extant albatrosses. We detail that a previously described early Miocene species, “Plotornis” arvernensis, should be expunged from the fossil record of albatrosses. However, the new fossils provide further evidence that the extant, mainly Southern Hemispheric, distribution of albatrosses is relictual compared with the past distribution of the total group (stem group crown group). With unambiguous records from the early Oligocene, early Miocene, and Pliocene, albatrosses are now known to have had a long evolutionary history in the European part of the North Atlantic, but the reasons for their extinction remain poorly understood.

A single fossil tarsometatarsus from the Etadunna Formation, of Late Oligocene—Early Miocene age, at the Snake Dam Locality in South Australia reveals the first pre-Pliocene record of anhingids in Australia. Anhinga walterbolesi sp. nov. provides the oldest record globally for the Anhingidae and, with the contemporary presence of stem-group phalacrocoracids in the same formation, indicates a probable Early Oligocene to Eocene age for the common ancestor of anhingids and phalacrocoracids.

Reliable estimates of population parameters derived from survey methods are essential for decision making in management of endangered species. We evaluated whether point-count surveys used in conjunction with occupancy and binomial mixture models (BMMs) constituted a reliable approach for monitoring the federally endangered Golden-cheeked Warbler (Setophaga chrysoparia) on a preserve in central Texas. Occupancy and abundance were estimated using point-count surveys conducted on each of five 113-ha detection grids in 2008 and seven grids in 2009. Single-season occupancy models and BMMs were used to estimate occupancy and abundance, respectively. Occupancy estimates per grid ranged from 0.48 to 1.0 in 2008 and from 0.52 to 1.0 in 2009. Estimates of abundance were compared with territory densities independently estimated using spot mapping, the standard by which all other avian survey methods are often compared. Abundance estimates produced by BMMs were significantly higher than territory density estimates at all but one site in 2008 and two sites in 2009. While estimation techniques incorporating detection probabilities should be considered in monitoring programs, our results suggest that BMMs deserve careful scrutiny before being used to estimate abundance or to monitor population trends.

Although food resources are thought to limit many populations, the extent to which the population dynamics of predators and prey are coupled is rarely known. We examined a sedentary population of Red Crossbills (Loxia curvirostra L. complex) that relies on seeds in cones that accumulate in the canopy of Rocky Mountain Lodgepole Pine (Pinus contorta latifolia Engelm.). Nearly constant annual seed production and gradual weathering over many years of initially impenetrable cones in the tree canopy results in a continuous and perhaps roughly constant replenishment of accessible seeds. However, seed availability varies seasonally. We estimated the seasonal variation in the energy demands of the study population. Our results demonstrate that seed predation by these sedentary Red Crossbills potentially drives the seasonal variation in seed availability and likely causes the Red Crossbill population to be regulated. The results are also consistent with a nearly constant replenishment of accessible seeds. In its apparent population stability this sedentary crossbill differs greatly from many other crossbills, which often vary in abundance by several orders of magnitude from year to year.

Recruitment is an important aspect of life history that is difficult to estimate without long-term data. We used 28 years of data to create multistate capture—mark—recapture models with maturity status as state to provide estimates of age-dependent probabilistic recruitment (transition from juvenile to breeder state) of Cassin's Auklets (Ptychoramphus aleuticus) breeding at Southeast Farallon Island, California. We found strong evidence for age effects in recruitment and survival, but not in breeding propensity. We also examined parental-age effects on return rate of offspring. Although an average of 70% of a cohort begins breeding by age 4, fledglings from 2- to 4-year-old mothers were less likely to become breeders than fledglings produced by older mothers. This may be attributable to age-related differences in egg production and maternal offspring-rearing abilities that could contribute to differences in fledgling recruitment rates. Eggs of younger mothers had lower volume and their fledglings had lower mass than those of older mothers. We suggest that researchers, managers, and population modelers consider the possibility that young breeding birds that successfully fledge young do not always produce viable offspring that will become breeders.

In lek mating systems, females visit aggregations of displaying males and appear to have unrestricted opportunity to choose and mate with any male. Behavioral observations of lekking birds indicate that females generally mate once and that only a small percentage of males gain a majority of copulations. However, genetic analyses of paternity have revealed that multiple males sometimes sire young within one brood. We analyzed paternity of 25 broods of Greater Prairie-Chickens (Tympanuchus cupido pinnatus) breeding in an isolated population in central Wisconsin. We found multiple paternity in 44% of broods (1–4 sires brood^-1) and a positive relationship between the number of sires and female home-range size prior to nesting. Multiple paternity was apparently not influenced by local breeding experience: native Wisconsin and translocated females from Minnesota did not differ in the likelihood of multiple mating. The high incidence of multiple paternity may reduce the variance in male reproductive success and increase the effective population size, which may be important for the maintenance of genetic diversity in small, isolated populations.

In many avian species, females do not nest the first year they attain sexual maturity. I examined the benefits and costs of delayed nesting in a nonmigratory population of Canada Geese (Branta canadensis) in New Haven County, Connecticut, from 1984 through 2008. I individually marked 381 female goslings and monitored them throughout their lives. Eighty-seven females were recruited into the local breeding population; 16 of these started nesting when 1 or 2 years old (young nesters), and 71 started nesting when 3 to 9 years old (delayed nesters). During their first reproductive effort, young nesters and delayed nesters produced similar-sized clutches but young nesters produced fewer hatchlings or fledglings. Young nesters died sooner than delayed nesters, but the two groups were similar in number of years of life following first nesting effort, number of nesting years during life span, and total lifetime production of eggs, hatchlings, and fledglings. Both young nesters and delayed nesters had similar values of λ^(m), which is an integrated measure of an individual's propensity fitness. Young nesters weighed more at fledging than delayed nesters, which suggests that larger and healthier females were more likely to become young nesters. Competition among Canada Geese for safe nesting sites on islands was keen in the study area. This may have contributed to the prevalence of delayed nesting because geese that were unable to secure a safe nesting site may have delayed nesting until the following year.

Knowledge of the relative contributions of predator species to overall rates of nest predation can improve our understanding of why predation risk varies, but the identity of predators is seldom known. We used video technology to identify nest predators of the tree-nesting Acadian Flycatcher (Empidonax virescens) and the shrub-nesting Indigo Bunting (Passerina cyanea) in forests of Missouri and southern Illinois. Raptors, snakes, and nonraptorial birds were the most frequent nest predators; rodents depredated fewer nests; and mesopredators rarely depredated nests. We tested hypotheses concerning effects of songbird species, ordinal date, nest stage, height, and age on overall and predator-specific predation rates to determine whether variation in overall predation rates was attributable to a subset of nest predators. Overall predation rates were higher for Indigo Buntings than for Acadian flycatchers, were higher during the nestling stage than during incubation, and exhibited a midseason peak. Compared with Indigo Buntings, Acadian Flycatchers experienced significantly lower predation by raptors, nonraptorial birds, and snakes and were never depredated by a mesopredator. Nests of both species had higher predation rates during the nestling stage than during incubation because of increased predation by raptors and snakes. Raptors, nonraptorial birds, snakes, and rodents all exhibited a midseason peak in predation rates. Estimating the contribution of specific predators to overall predation rates can increase our mechanistic understanding of why predation risk varies and thus improve our understanding of antipredator behavior and increase our ability to predict how anthropogenic habitat and climate change will influence avian productivity.

We present the first molecular phylogenetic hypothesis for Knipolegus (black-tyrants), a widespread genus of South American tyrant-flycatchers, based on nuclear and mitochondrial DNA sequences. Bayesian and maximum-likelihood analyses support three clades within Knipolegus, one confined to northern South America, one confined to southeast Brazil, and one confined to the Southern Cone and southern Andes. Within each clade, two or more species are broadly sympatric or parapatric, overlapping in general distribution but differing in habitat specialization. Maximum-likelihood ancestral state reconstructions using an equal-rate stochastic model support a single origin of austral migration in the southern group. Contrasting with these strong geographic patterns, ancestral state reconstructions of plumage and display evolution were more complex, with multiple inferred character-state changes. Ancestral state reconstructions suggest a sexually dimorphic ancestor of Knipolegus, and sexually similar plumages are the result of three independent character-state changes: one in male plumage and two in female plumage. Ancestral state reconstructions support the conclusion that flight displays with mechanical sounds originated in the Knipolegus ancestor, and loss of mechanical sounds in flight displays occurred twice.