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Cognition includes the acquisition, processing, retention of, and acting upon information from the environment. Avian cognition has been investigated by the approaches of experimental psychology and in the context of specific tasks, such as spatial memory. However, the costs and benefits of cognitive ability have not been considered in a life-history context. I explore possible relationships between behaviors that might indicate cognitive function and other attributes, particularly brain size, rate of development, age at maturity, and life span. Large brain size and prolonged development are seen as potential costs of intelligent behavior. Long life span may permit the extended learning periods that support experienced-based cognitive function. Play behavior, which plausibly supports the development of motor and social skills, and, to a lesser extent, foraging innovations, are related to brain size. The challenge of foraging in a spatially and temporally varying environment, experienced for example by pelagic seabirds, is associated with prolonged embryonic development. Although these connections lack mechanistic foundations, they suggest that cognition can be considered as a part of the life history of the individual and that potential costs of cognition might provide guidelines for directing the comparative study of intelligent behavior.
Geophagy is widespread and well documented for mammals, but avian geophagy has only recently become the subject of serious scientific investigation. I analyzed data from 606 mornings of observations at a large avian geophagy site or “clay lick” in the southwestern Amazon Basin to examine the effects of weather on bird lick use. Birds used the clay lick on 94% of the mornings without precipitation or fog. Parrots dominated the site in both numbers of species (17) and individuals (>99%). Weather conditions were significantly correlated with total lick use: there was greater use on sunny mornings and less on rainy mornings. Fog and overnight rain were correlated with low lick use. Sun, rain, fog, and overnight rain were recorded on 47, 25, 20, and 8% of the mornings, respectively. I estimated that inclement weather caused an annual 29% reduction in geophagy for all bird species combined. When early morning rain prevented species from using the lick, they did not return later in the day nor did they compensate for rainy mornings by increasing lick use on subsequent days. The timing of lick use and the lack of compensation suggest that neutralization of toxins could be driving lick use in this system.
We monitored the heart rates of free-living Tule Greater White-fronted Geese (Anser albifrons elgasi) during human disturbances on their wintering range in the Sacramento Valley of California during 1997. We used implanted radio transmitters to record the heart rates of geese as an observer experimentally approached them at a constant walking speed. On average, geese flushed when observers were 47 m (range: 25–100 m) away. Change point regression was used to identify the point in time when heart rate abruptly increased prior to flushing and when heart rate began to level off in flight after flushing. Heart rates of geese increased as the observer approached them during five of six disturbance trials, from 114.1 ± 6.6 beats/min during the observer's initial approach to 154.8 ± 7.4 beats/min just prior to flushing at the first change point. On average, goose heart rates began to increase most rapidly 5 sec prior to taking flight, and continued to increase rapidly for 4 sec after flushing until reaching flight speed. Heart rate was 456.2 ± 8.4 beats/min at the second change point, which occurred immediately after flushing, and 448.3 ± 9.5 beats/min 1 min later during flight. Although goose heart rates increased as an observer approached, the largest physiological change occurred during a 9-sec period (range: 1.0–15.7 sec) immediately before and after flushing, when heart rates nearly tripled.
Most of what is known about diet of Xantus's Murrelets (Synthliboramphus hypoleucus) comes from prey found in 19 of 22 murrelet stomachs collected during the 1977 breeding season near Santa Barbara Island in the Southern California Bight (SCB). In May 2002, we examined stomachs of 10 Xantus's Murrelets collected near Anacapa Island, also within the SCB. Seven of the 10 stomachs contained prey. Prey were subadult or adult northern anchovy (Engraulis mordax; 2 stomachs), either juvenile bluefin driftfish (Psenes pellucidus) or medusafish (Icichthys lockingtoni; 2 stomachs), and euphausiids (Thysanoessa spinifera; 3 stomachs). Only one prey type was found in each stomach. Our sample added to the diversity of known prey types used in the SCB, including euphausiids and larger age/size classes of fish. We confirmed continued use of northern anchovy, and identified new prey species (bluefin driftfish or medusafish) associated with jellyfish or floating algae and debris in convergence lines. During the breeding season, Xantus's Murrelets appear to be generalist feeders that search for and use available prey that may be concentrated at convergence lines.
We radio-tagged 55 Pacific Golden-Plovers (Pluvialis fulva) in spring 2001–2003 on wintering grounds in Hawaii. Following their northward migration (most birds deserted winter territories in late April), we relocated 15 golden-plovers in three regions of Alaska: Copper River Delta, King Salmon, and Kotzebue. One individual made the transpacific flight from Oahu to the Alaska Peninsula in a minimum time of 70 hr at a minimum flight speed of 56 km/hr. Our findings, together with earlier records, indicate a major Hawaii-Alaska migratory connection for this species, and suggest that plovers wintering on Oahu nest throughout the known Alaska breeding range. Post-breeding, 84% of the sample birds returned to Oahu and reoccupied their previous winter territories.
We report on behavioral interactions between fire ants (Solenopsis invicta) and vertebrate predators at two Black-capped Vireo (Vireo atricapilla) nests at Fort Hood, Texas. In the presence of fire ants, an eastern woodrat (Neotoma floridana) failed to depredate a clutch of vireo eggs at one nest, while a rat snake (Elaphe obsoleta lindheimeri) depredated nestlings at another nest, despite fire ants swarming the nest. Neither nest was successful. Direct and indirect effects of interactions among nest predators on avian nesting success need further assessment.
Decades of fruitful research on the study of vocal communication in birds have provided surprisingly little evidence of a predation cost associated with singing. In this paper, I report the first observational evidence of a risk of predation associated with chorusing in a Neotropical wood-quail. Black-breasted Wood-Quail (Odontophorus leucolaemus) live in groups year-round and produce coordinated group choruses or duets. Three mammalian and two avian species of predators were attracted to playbacks of recorded wood-quail choruses that I used during population surveys and capture attempts from March to August, 2000–2002. The trade-off between signaling and predation risk may be an important force in the evolution of chorusing in New World quails.
In broods of Crested Ibis (Nipponia nippon), aggressive dominance was unstable over time, even within feeding sessions. All chicks took turns pecking aggressively while broodmates hung their heads submissively, although roles were contested at the start of feeding bouts when chicks were 11–17 days old. In all broods, at least half of all pecks were false pecks, which did not strike broodmates even when within reach. False pecks seem to be ritualized displays that function to solicit food from parents and possibly to threaten rivals.
Several standard references report the incubation period of the Bar-tailed Godwit (Limosa lapponica) as 20–21 days, but the source of those statements is unclear and may be based on speculation. Here, I report an incubation period at a nest in Alaska that was estimated to be between 21.7 and 23.8 days. This is consistent with incubation periods of three other species of godwit, which are reported to be 22–26 days. At the Alaskan nest, both sexes incubated and would not flush until approached within about 0.6 m. No special displays were observed when the male relieved the female at the nest. The chicks departed the nest when less than 1 day old.
Geese are normally herbivorous. I report an instance of Canada Geese (Branta canadensis) feeding on alkali flies (Ephydra hians) at hypersaline Mono Lake, California. The bout was brief and possibly represented exploratory behavior by inexperienced birds.
Cannibalism is uncommon in birds, and instances of adults killing and eating other adults are especially rare. Cases of intraspecific predation among passerines constitute a very small percentage of published reports, and many of the cases are based on circumstantial evidence. In July 2001, I witnessed a group of Northwestern Crows (Corvus caurinus) kill and consume a conspecific adult in Olympic National Park, Washington. I am aware of no other published reports of adult-adult cannibalism for this species or the Corvidae family.
Instances of coprophagy by birds are rare in comparison to coprophagy by other animals such as mammals and insects. Here, I report on White-winged Crossbills (Loxia leucoptera) obtaining forage from river otter (Lontra canadensis) feces in Kouchibouguac National Park, New Brunswick, Canada. In sequence, two male White-winged Crossbills landed on a scat, pecked at it, and ingested small pieces before flying away. The birds may have been feeding on fish bones or undigested fish present in the feces.
We report on an unusual nest site of a Semipalmated Plover (Charadrius semipalmatus) at La Pérouse Bay, Manitoba, Canada. The nest was located at the base of a 41-cm-high willow (Salix spp.) in a dense willow patch surrounded by coastal mudflats. Vegetation height and percent visual obstruction at the nest site were unusually high compared to height and cover previously described for Semipalmated Plovers. The nest was successful (≥2 eggs hatched). The discovery of this unusual nest site in dense vegetation suggests that some Semipalmated Plover nests may be overlooked, emphasizing the need to conduct thorough searches even in non-traditional habitats among shorebird species that typically nest in open habitats.
We report on the discovery of a distinct female song in Nava's Wren (Hylorchilus navai), similar to that recently discovered in Sumichrast's Wren (Hylorchilus sumichrasti). In both species, females sometimes countersing with males but do not combine their songs into a synchronized duet as in many other tropical wrens. We provide observations that suggest territorial defense, intra-pair contact, and perhaps mate-guarding as possible functions of female song in Hylorchilus, a little-known genus endemic to Mexico.