Vocal behavior in tropical hummingbirds is a new area of study. Here, we present findings on the vocalizations and associated behaviors of two species: Sombre Hummingbird (Aphantochroa cirrhochloris) and Rufous-breasted Hermit (Glaucis hirsutus). These are the only hummingbirds in which the brain areas activated by singing have been demonstrated. They are also among the basal species of their respective subfamilies, Trochilinae and Phaethornithinae and, thus, represent early stages in the evolution of hummingbird vocal communication. We found that the two species exhibit distinctive vocalizations and behaviors. Sombre Hummingbird calls had more modulation and were often used during agonistic interactions, whereas Rufous-breasted Hermit calls had higher pitch and purer tones and were produced in less aggressive interactions. Sombre Hummingbird song was highly stereotyped in syllable structure and syntax, whereas Rufous-breasted Hermit song was highly variable. Comparative analysis points to consistent similarities in use of vocalizations by the Sombre Hummingbird and other trochilines, and by the Rufous-breasted Hermit and other phaethornithines. We hypothesize that differences in vocal behavior between hummingbird lineages arise as adaptations to their foraging strategies.
Bile salts are the major end-metabolites of cholesterol and are important in lipid digestion and shaping of the gut microflora. There have been limited studies of bile-salt variation in birds. The purpose of our study was to determine bile-salt variation among birds and relate this variation to current avian phylogenies and hypotheses on the evolution of bile salt pathways. We determined the biliary bile-salt composition of 405 phylogenetically diverse bird species, including 7 paleognath species. Bile salt profiles were generally stable within bird families. Complex bile-salt profiles were more common in omnivores and herbivores than in carnivores. The structural variation of bile salts in birds is extensive and comparable to that seen in surveys of bile salts in reptiles and mammals. Birds produce many of the bile salts found throughout nonavian vertebrates and some previously uncharacterized bile salts. One difference between birds and other vertebrates is extensive hydroxylation of carbon-16 of bile salts in bird species. Comparison of our data set of bird bile salts with that of other vertebrates, especially reptiles, allowed us to infer evolutionary changes in the bile salt synthetic pathway.
Despite their large vocal repertoires and otherwise highly versatile singing style, male mockingbirds sometimes sing in a highly repetitive fashion. We conducted a playback experiment to determine the possible signal value of different syllable presentation patterns during simulated male intrusions in the Tropical Mockingbird (Mimus gilvus) testing the hypothesis that more repetitive singing represents a stronger threat and generates a stronger aggressive response. Responses were measured in terms of approach and singing behavior and were analyzed using McGregor's (1992) multivariate method. We also introduce the use of survival analysis for analyzing response variables for which subjects do not perform the behavior in question in at least one of the replicates (known as 'right-censored variables' in the statistical literature). As predicted by theory, experimental subjects responded more aggressively to songs composed of a single note than to variable ones. However, versatility at the between-song level had an opposite effect as high song switching rates generated stronger responses than low ones. Given the lack of a statistical interaction between within-song versatility and switching rate, we conclude that these two parameters may serve independent purposes and possibly transmit different information. We discuss the possibility that the signal value of variation in vocal versatility lies in the mediation of territorial conflicts, the attraction of female partners and/or the mediation of conflicts over access to reproductive females.
—Timing of breeding in Florida Scrub-Jays (Aphelocoma coerulescens) varies both within and between years. Social status and breeding experience may explain much of the within-year variation,
but the availability of certain foods may partially explain between-year patterns. Scrub-jays in suburban habitats with access
to unlimited human-provided foods breed earlier and with less between-year variation in timing of breeding than jays in wildland
habitats. We hypothesized that those differences in timing of breeding result from access to human-provided foods in the suburban
site. Human-provided food may influence timing of breeding by improving the overall body condition of females, or it may influence
breeding by providing nutrients essential for breeding. If condition mediated, breeding females in the two habitats should
differ in certain physiological parameters relative to time before egg laying and calendar date. If the effect is not related
to body condition, we expect differences in pre-breeding females relative to calendar date, but not in relation to time before
egg laying. To test those predictions, we measured plasma levels of total protein, calcium, luteinizing hormone, and estradiol.
We also measured variables associated with body condition—body mass, a size-corrected condition index, and total body lipids.
Most variables tended to increase with both days before laying and calendar date, except total body lipids, which decreased.
Suburban females had higher levels of plasma protein relative to both days before egg laying and calendar date than female
breeders in the wildland habitat. Luteinizing hormone differed between sites relative to calendar date but not days before
laying. Our data suggest that suburban scrub-jays with access to predictable sources of high-quality human-provided foods
accumulate endogenous protein that can be used to breed earlier. Received 25 January 2002, accepted 14 June 2003.
The basal metabolic rates (BMR) of 4 Apapane (
Himatione sanguinea) birds who were maintained in an outdoor aviary for a year were compared to 4 Ss freshly caught. Data indicate that the length of time aviary Ss were held in captivity had little effect on the BMR but that the length of time they were fasted before their BMR was measured had a pronounced effect. Results contradict those of R. E. MacMillen (1981). (11 ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Observed the foraging strategies and predator–prey relationships of humpback whales in Frederick Sound, Alaska. Seabirds were excellent indicators of the local presence of prey; therefore, the authors monitored and recorded bird identity, abundance, location, and behavior. Many birds, especially the Bonaparte's gull, herring gull, and including the Cassin's auklet, cued on surface-feeding whales, with flocks of substantial size repeatedly moving to where humpbacks surfaced. Findings indicate that subsurface feeding associations occurred between diving birds and whales and that the observed ingestion of auklets by the whales was incidental. (4 ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Examined the incidence of fault bars (FBs) in the feathers of an experimental population of white-crowned sparrows (
Zonotrichia leucophyrys gambelii) and the correlation with dietary concentrations of the sulfur-containing amino acids (SAAs) cystine and methionine. The incidence of FBs and the distance between them were alike in both groups of Ss given SAA, suggesting FBs were not attributable to low dietary SAA concentrations. FBs were rare in Ss residing in large aviaries with minimal disturbance and in those caught during autumn migration, suggesting that the stress of handling induced the formation of FBs in experimental Ss. (11 ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)
The development of social behavior may be traced through physiological and chemical agencies eventually to genetic factors. Hence the basis for social reactions is developed largely in the embryo before hatching. Vocalization is used as an example of early post-hatching social interaction between the mother hen and her chicks. Two types occur in newly hatched chicks, pleasure notes and distress calls. A study of the conditions leading to the appearance of each "suggest the existence of two antithetical neural systems balanced against each other, and corresponding to what in man would be called security-insecurity feelings and responses." Parent birds act as socializers in many phases of the youngs' life as is suggested by the lesser survival of incubator-hatched, pen-raised birds as compared to wild trapped stock after transplantation. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Observed pair bonding among bufflehead ducks involving the same partners 2–3 yrs consecutively, noting that males abandoned their mates during molting season only to reunite later. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Describes 3 distinct types of nest-searching behavior noted during field studies of brown-headed cowbirds (Molothrus ater) in Ontario, Canada, from 1970 to 1973. The 3 habitat-specific nest searching strategies were (a) cryptic, silent watching of nest-building hosts in semiopen habitats; (b) secretive searching by walking on the ground in dense woods; and (c) active, intentionally noisy searching in dense shrubbery along forest edges and garden hedges. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Examined variation in the calls and facial patterns of cliff swallow (
Hirundo pyrrhonota) chicks at least 18 days old to test the prediction that in species in which dependent young intermingle, coloniality necessitates parent–offspring recognition and thus favors the evolution of highly variable "signature" traits. Ss' calls were highly distinctive: Interindividual variation was significantly greater than intraindividual variation for 5 measured parameters. Playback experiments indicated that parents could locate their chicks by these signature calls alone. Chick faces were also individually distinctive and could be readily distinguished by human observers, although the authors did not test whether or not parents actually used this information. Studies of several swallow species implicate coloniality as the variable in this family that separates species with distinctive chick signatures and strong parental recognition. (12 ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Presents field data on feeding and scanning behavior of crossbills (
Loxia leucoptera) in relation to flock size (FS). Feeding rates (FERs) increased and individual vigilance decreased as FS increased from 1 to 2. Further increases in FS did not correspond with substantial reductions in individual vigilance, but did correspond with frequent agonistic interactions (AIs). As rates of AIs increased, FERs of subordinate age-sex classes declined relative to those of dominant age-sex classes. Rates of AIs were higher when crossbills foraged on conifers whose cones were compactly dispersed. Flocks were smaller when rates of AIs were high and conifers had compact cone dispersions. FS increased as seed density declined. Larger flocks, with high levels of collective vigilance, were favored because FER and the time spent scanning while seeds were husked also declined. Crossbills that forage on small-crowned conifers are more sexually dichromatic and have other traits indicating stronger sexual selection than crossbills that forage on large-crowned conifers. It is suggested that these differences result from differences in rates of AIs, which influence female FERs compared with male FERs, and likely have a differential effect on female mortality rates and the population sex ratio. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Conducted 3 experiments in which 3 barn owls and 3 screech owls were presented with an active or inactive (dead) brown or white mouse. Active mice were significantly (p < .01) preferred as the 1st choice of prey. The differential predation is considered in terms of visual cues. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Reports the experimental use of a tetracycline marking technique during a study of nesting Wood Ducks (
Aix sponsa) within a green-tree impoundment at a wildlife refuge. Results indicate that tetracycline declomycin, when given intraperitoneally and at relatively low dosage, works safely and effectively to mark the eggshells of laying fowl so that egg-laying patterns may be studied. (9 ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Observed the spot-winged falconet (
Spiziapteryx circumcinctus) roosting and breeding in monk parakeet's (
Myiopsitta monachus) communal nests; observations were made in Cordoba Province, Argentina. Findings indicate that the falconet used the parakeets' nests for roosting in winter and for breeding in summer. Results indicate that unlike the African pigmy falcon's (
Polihierax semitorquatus) relationship with the sociable weaver (
Philetairus socius), the spot-winged falcon does not benefit the monk parakeet in any way. (4 ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Investigated the stability of parent–offspring and sibling–sibling bonds among neck-banded greater white-fronted geese in the wild. Offspring associated with their parents for longer periods of time than reported for other geese, with 69% of yearlings, 39% of Ss aged 2 yrs, and 38% aged 3+ yrs remaining with their parents. Older offspring with young occasionally rejoined their parents. Sibling bonds persisted after the 1st yr of life, with siblings maintaining social contact at 1–3 yrs of age and older. Older offspring were more likely to associate with brood mates than with parents. Incidental sightings in subsequent years revealed that some offspring up to 8 yrs old associated with their parents and/or siblings. Older offspring and parents may benefit by remaining together if extended families are more dominant and have better access to limited food and safe roost sites. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Friarbirds and orioles are convergently similar in ecology and morphology and belong to a guild of birds that feed together and that display much aggression toward each other. Within this guild, mimics are spared from attack by larger models. The larger the friarbird compared to the oriole, the more perfect is the mimicry. These attacks among birds provide a selective force for evolution of size-related mimicry. (36 ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Comparative analyses constitute an important complement to studies of adaptive behavior. Previous studies of avian mating systems considered the role of paternal care and habitat type on the evolution of polygyny. We extended those studies and included in our analyses the role of habitat quality, as characterized by food supply. Species in the monophyletic lineage of acrocephaline warblers (Acrocephalus, Chloropeta, Hippolais) are widely distributed, inhabit a variety of different habitats, and show a variety of breeding systems. We present a phylogenetic analysis of parental care and mating system characteristics in relation to ecological traits in 17 species. On the basis of a molecular phylogeny, we reconstructed patterns of changes from social monogamy to polygyny, and in paternal brood care. Specifically, we analyze the coevolution of brood care participation of males and social system, and how it relates to habitat quality. Furthermore, we assessed the phylogenetic inertia of mating systems. We found support for the hypothesis that change to highly productive habitats was associated with a greater emancipation of males from brood care, and with polygyny and promiscuity. Poor habitats, on the other hand, were associated with monogamy and the occurrence of helpers. In contrast to some morphological characters, mating systems appear to be phylogenetically labile.
The major body components (water, lean dry, and fat) were measured in the carcasses of Gray Catbirds from which the flight muscles had been removed. Birds were collected from May through October near Ann Arbor, Michigan and during September and October near Gainesville, Florida. Additionally, the glycogen content of muscle and liver and the concentrations of glucose and triglycerides in plasma were determined in catbirds sampled during fall migration in Florida. Catbirds attained maximum body masses of ∼50 g in Florida, largely due to the addition of fat. Relatively lean birds (∼3-4% body fat) in spring through fall weighed approximately 35 g. Thirteen percent of the birds sampled were estimated to have had sufficient reserves of fat to cross the Gulf of Mexico, although a larger proportion of the population probably makes this crossing. The lean dry mass of the carcass (without the flight muscles) is related significantly to structural body size and time of day, but is not related to molt, sex, or carcass fat content. Plasma glucose and triglycerides in free-living fall migrants do not vary diurnally. Liver glycogen, however, is four times higher in the evening than in the morning (77 and 19 mg/g, respectively), and muscle glycogen is five times higher in the evening (20 and 4 mg/g, respectively). Evening concentrations of glycogen are among the highest values reported for birds and do not confirm the reduction in glycogen reported for some other migrants.
In oviparous reptiles, incubation temperature has been shown to have profound effects on embryonic development and hatchling phenotypes. However, these effects are not well studied in birds, because they typically brood their eggs within a narrow range of temperatures. The Australian Brush-turkey (Alectura lathami) is a megapode that constructs incubation mounds and relies on the heat produced by respiring microorganisms in these mounds to incubate its eggs and is, therefore, a useful comparative model. We developed a new method for monitoring mound and egg temperature to determine both mound thermal variability and the thermal tolerance of embryos. All mounds exhibited greater temperature fluctuations than previously reported or predicted by modeling. Furthermore, all Australian Brush-turkey embryos were exposed to suboptimal temperatures for prolonged periods during development, some experiencing temperatures 6°C above or 9°C below the optimum (34°C) for 12 h. This is the first evidence of bird embryos developing during long-term exposure to suboptimal temperatures. Notably, natural incubation periods were 2–6 days shorter than previously reported for this species.
Mitochondrial DNA (mtDNA) control-region sequences of 52 migratory and wintering Dunlins (Calidris alpina) from around the world were determined with direct sequencing of PCR products. The genetic lineages detected in these birds are identical to those found previously in a much larger sample of 155 breeding Dunlins from their northern circumpolar range. Samples of nonbreeding Dunlins from both sides of the Pacific reveal a mixture of two lineages that breed separately in eastern Siberia and Alaska. The presence of Dunlins with an eastern Siberian haplotype along the west coast of North America indicates that the Bering Strait does not represent a biogeographic barrier to Dunlin migration. Dunlins wintering in eastern Asia most likely originated from the discrete breeding population in northern Alaska because they possess haplotypes that were found predominantly in birds from this region. Similarly, Dunlins front staging and wintering sites in Europe and western Asia reveal a mixture of two mtDNA lineages that were previously found confined largely to European and central Siberian breeding grounds. Limited gene flow between these breeding areas, however, precludes definitive allocation of individuals to their population of origin on the basis of mtDNA analysis alone. Body mass, time of migration, and molting pattern seem to be associated with the mtDNA types of migratory Dunlins in Europe, but data are too sparse to determine whether these characters are useful adjuncts in assigning nonbreeding birds to populations that correspond to the major genetic lineages. Overall, the genetic composition of nonbreeding populations indicates the confluence of breeding populations on southward migration. Because of strong phylogeographic population structure in Dunlins on their breeding grounds, mtDNA analysis can be extremely useful in defining broad migration corridors or flyways, and in determining staging and wintering areas used by the major breeding populations.