Search

Generalist species are more successful than specialists in anthropogenically modified environments or in environments in which they have been introduced, but the nature of the link between generalism and establishment success is unclear., A higher feeding innovation rate has previously been reported in habitat generalist birds from North America. By allowing them to exploit new resources, this higher feeding innovation rate might explain the generalists' advantage. This result might be due to generalists being more likely to find new resources because they are exposed to more diverse environmental conditions. Alternatively, they might differ from specialists in other traits, in particular cognitive skills that might allow them to innovate more complex food searching and handling techniques., To test these hypotheses, we separated avian feeding innovations into a 'technical' (novel searching and handling behaviour) and a 'food type' (incorporation of a new food in a species' diet) category. Technical innovations, but not food type innovations, have previously been shown to correlate with avian brain size, suggesting they reflect cognitive ability. We used a world-wide data base of 2339 feeding innovations recorded in the literature, covering a total of 765 avian species and assessed the correlations between brain size and feeding innovation rates on one side and habitat and diet generalism on the other., Habitat generalism was positively related with food type innovation rate, but not technical innovation rate or brain size. This suggests that habitat generalist species are more likely to incorporate new food types in their diet because of higher chances to find new food resources in their environment, or of a higher opportunism, but not enhanced cognitive skills. In contrast, diet generalist species had higher food type and technical innovation rates, as well as larger brains, suggesting that cognitive skills might help species expand their diet breadth or that an increase in diet breadth might favour the evolution of enhanced cognitive abilities., Our results provide new insights into the nature of the generalists' advantage in the face of environmental changes, and suggest that dietary and habitat generalism are different, but convergent, routes to feeding flexibility and adaptation to changed environments. [ABSTRACT FROM AUTHOR]

Copyright of Revista Mexicana de Biodiversidad is the property of Universidad Nacional Autonoma de Mexico, Instituto de Biologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The article presents a study on the effect of phenological change on the spring and autumn migration of North American raptors. The researcher conducted the project in the Whitefish Point Bird Observatory and Hawk Ridge Bird Observatory in North America. He concludes the timing is earlier in spring and later in autumn.

It is well documented that irruptive and nomadic migrants move in response to resources that are distributed unpredictably in space, time or both. Increasing evidence, however, suggests that irruptive and nomadic species may use seasonal timing mechanisms to prepare for migrations, despite the more facultative nature of their movements. Here we use data from free-living and captive Red Crossbills Loxia curvirostra, a typical irruptive nomad, to examine three hypotheses regarding control of facultative migration: (1) the facultative migration hypothesis, which states that both preparation and departure decisions are regulated by resource availability; (2) the seasonal preparation hypothesis, which states that preparation is initiated by seasonal factors (i.e. endogenous rhythms and/or photoperiod) but that departure decisions are dependent on local resource availability; and (3) the seasonal migration hypothesis, which states that both preparation and departure decisions are initiated by seasonal mechanisms and are independent of local food resources. Red Crossbills in North America are thought to make temporally consistent spring migrations in anticipation of conifer cone maturation. In this study, fat deposits of free-living Red Crossbills peaked in May and June, exceeding even winter deposits. In agreement with the field data, captive birds on a natural photoperiod with constant food and temperature showed a peak in fat deposition and activity levels in June. These findings are consistent with the seasonal preparation and the seasonal migration hypotheses and contribute to a growing literature that suggests that facultative migrants may prepare for movements in similar ways to seasonal migrants. [ABSTRACT FROM AUTHOR]

Migration can take place primarily during the day or at night, or during both depending on the species. Why the timing of migration varies among species has been the object of much research but the underlying ecological processes are still unclear. Proximally, migration timing may be influenced by the timing of other activities or may be more prevalent in species that migrate over long distances. Adaptive scenarios emphasize the reduction in flight costs at night especially in smaller species and the advantages of travelling in groups during the day to locate staging sites more efficiently. I used phylogenetic independent contrasts to examine these hypotheses in all North American nesting birds. I uncovered 24 evolutionary transitions in migration timing, most of which involved a switch from nocturnal to diurnal migration. Few of these transitions involved a concomitant change in the timing of foraging habits or migration distance. However, species in diurnal clades were larger, travelled in larger flocks and were generally more sociable than their nocturnal counterparts. The results support the hypotheses that a reduction in flight costs and the ability to pool information from companions are associated with migration timing in North American bird species. [ABSTRACT FROM AUTHOR]

Numerous hypotheses have been developed to explain how a brood parasite selects a host nest into which it lays its eggs. Most hypotheses address various aspects of nest placement. We used an extensive dataset to tease apart the relative strength of various hypotheses associated with nest placement and timing. These data were from North American tallgrass prairie and included nearly 2,000 nests of 17 host species known to accept eggs of the brood parasitic Brown-headed cowbird Molothrus ater. Regression tree analyses, with host species as a categorical covariate built around successive logistic regressions, implied that the 'edge effect' and 'perch proximity' hypotheses, the latter assessed as distance to woody vegetation, received the strongest support. Hypotheses concerning nest height, livestock proximity, habitat density, nest exposure, laying date, and host clutch size received weaker or subsidiary support, the latter meaning that the hypotheses received significant support only after edge effects or distance to woody vegetation were accounted for first. Host species was associated significantly with parasitism rate, but host species was itself correlated with various vegetation and landscape variables that we assessed. Brood parasitism rate and nest height were associated non-linearly. In addition to a clear hierarchical pattern among factors associated with rates of parasitism, several key explanatory variables had marked interactions, such as prairie edge and extent of woody vegetation or nest height and nest exposure. Such interactions, including between host species and certain landscape and vegetation variables, such as nest height and distance from woody vegetation, suggest caution is warranted when assessing the various competing hypotheses, which are not mutually exclusive. [ABSTRACT FROM AUTHOR]

Species distribution models are a fundamental tool in ecology, conservation biology, and biogeography and typically identify potential species distributions using static phenomenological models. We demonstrate the importance of complementing these popular models with spatially explicit, dynamic mechanistic models that link potential and realized distributions. We develop general grid-based, pattern-oriented spread models incorporating three mechanisms—plant population growth, local dispersal, and long distance dispersal—to predict broad scale spread patterns in heterogeneous landscapes. We use the model to examine the spread of the invasive Celastrus orbiculatus (Oriental bittersweet) by Sturnus vulgaris (European starling) across northeastern North America. We find excellent quantitative agreement with historical spread records over the last century that are critically linked to the geometry of heterogeneous landscapes and each of the explanatory mechanisms considered. Spread of bittersweet before 1960 was primarily driven by high growth rates in developed and agricultural landscapes, while subsequent spread was mediated by expansion into deciduous and coniferous forests. Large, continuous patches of coniferous forests may substantially impede invasion. The success of C. orbiculatus and its potential mutualism with S. vulgaris suggest troubling predictions for the spread of other invasive, fleshy-fruited plant species across northeastern North America. [ABSTRACT FROM AUTHOR]

Paridae are among the bird families benefiting from food storing. However, not all its members hoard food. Our objective was to clarify the role of ecological factors in occurrence of food storing. We reviewed the data on major ecological characteristics of the Paridae species and analysed their association with the presence/absence of food storing. Our statistical model revealed that geography (distribution in North America) and taxonomy (genus Poecile) are better predictors of food storing than any of the studied ecological traits. Nevertheless, food-storing Poecile species inhabit mixed or coniferous woodlands with seasonal richness of food, while non-storing species tend to prefer edge and open habitats, where alternative food sources are available. Sociality and territoriality outside breeding season coincides with food storing. The analysis performed within the Baeolophus– Lophophanes– Periparus– Poecile clade with ancestral food storing revealed no factor except continental climate that would explain the persistence of food storing. The phylogenetic analysis of ancestral states of the studied characters allowed us to propose a possible scenario for the emergence of food storing in Paridae. (1) Food storing is not ancestral in Paridae and appeared only once in the common ancestor of the Baeolophus– Lophophanes– Periparus– Poecile group. (2) According to estimation of molecular clock in Paridae, food storing appeared before their radiation in North America. [ABSTRACT FROM AUTHOR]

The article presents an analysis of American Kestrels migration counts in 20 autumn hawkwatch sites in North America to estimate the population trends. It states that in the eastern part, significant declines was noted from 1974-2004, which was along the Appalachian Mountains and the Atlantic Coast, while stable numbers in eastern Great Lakes, and a noteworthy increase in western Great Lakes regions. It mentions that the study indicates population decline along the Pacific Northwest and the western interior of North America. Migration counts across the Gulf of Mexico were also included, which shows no significant population changes. The study suggests that kestrel populations had a long-term decline along the northeastern, western, and midwestern parts of North America.

I report a case of snow bathing by House Finches (Carpodacus mexicanus), apparently the first for this species. As many as 15 finches bathed together, three to four at a time, in 18 cm of fresh loose snow in a manner typical when birds bathe in water or dirt: wings fluttered near the sides to spray the snow over the body with back and head plumage erected while the breast was pressed into the snow. Relatively few accounts of birds bathing in snow have been published. I found 23 prior reports of snow bathing for 16 North American species, mostly Passeriformes but including Falconiformes, Galliformes, Strigiformes, and Piciformes. Bathing in loose or uncompacted snow occurred more often than in wet or crusted snow, and there was a tendency for more than one bird to engage in snow bathing during each event. Brevity of accounts prevented identification of other factors that may be frequently associated with snow bathing. Bathing in snow is a routine behavior for some bird species, such as ptarmigan, and European accounts indicate that it is undoubtedly more widespread among North American species than shown by review of the literature. [ABSTRACT FROM AUTHOR]

Individual variation in stable behavioural traits may explain variation in ecologically relevant behaviours such as foraging, dispersal, anti-predator behaviour, and dominance. We investigated behavioural variation in mountain chickadees, a North American parid that lives in dominance-structured winter flocks, using two common measures of behavioural profile: exploration of a novel room and novel object exploration. We related those behavioural traits to dominance status in male chickadees following brief, pairwise encounters. Low-exploring birds (birds that visited less than four locations in the novel room) were significantly more likely to become dominant in brief, pairwise encounters with high-exploring birds (i.e. birds that visited all perching locations within a novel room). On the other hand, there was no relationship between novel object exploration and dominance. Interestingly, novel-room exploration was also not correlated with novel object exploration. These results suggest that behavioural profile may predict the social status of group-living individuals. Moreover, our results contradict the idea that novel object exploration and novel-room exploration are always interchangeable measures of individuals'' sensitivity to environmental novelty. [Copyright &y& Elsevier]

Penguins, Southern Hemisphere birds, were introduced to the Northern Hemisphere several times in the 1930s. None of the four species introduced became established but some individuals survived for at least a decade. Humboldt Penguins (Spheniscus humboldti) were observed in waters off the west coast of North America several times in the 1970s and 1980s and one was caught in a fishing net in Alaska in 2002. Penguins theoretically might be able to swim to suitable habitat in the Northern Hemisphere, but we argue the most likely explanation for their arrival in the Pacific Northwest was by fishing boat. [ABSTRACT FROM AUTHOR]

The article focuses on the refueling by long-distance migrant calidridine sandpipers traversing the interior of North America en route to Arctic and sub-Arctic breeding grounds. Perspectives from the evolutionary past and the influences of a strongly seasonal climate should be examined to understand the current status and speculate about the future of migration stopover habitats in interior North America. Molecular studies of migratory birds have revealed the profound effects that Pleistocene glaciations have had on the current genetic architecture of birds breeding in the northern hemisphere.

Presents information on a study which examined whether eruptions of boreal seed-eating birds in North America are synchronized and occur at regular intervals. Methodology; Results and discussion.

Focuses on a study which examined the effects of ecological disturbances to the behavior and survival of pheasants in North America. Observation on several female ring-necked pheasants that associated with farm operations, hunting, weather, and other movements; Details on the extended movements of hens and their survival mechanisms in a hazardous landscape.

1. During two fall migration seasons, a large number of flying targets were tracked by a radar mounted on an oceanographic research vessel. Observations were made in September and October in a region extending from the New England coast to the area south and east of Bermuda (Figs. 1 and 3). Accurate local wind measurements were made at short intervals during the observations. 2. Evidence was obtained that many of the targets were birds engaging in migration between coastal North America and the neotropics. Such birds often appeared in discrete 'waves' associated with cold fronts passing the North American coast. Distant from land, long periods occurred between 'waves' when no targets were observed. 3. Other targets, which were probably also migrating birds, flew in directions which were difficult to explain, or flew at speeds relative to the air which were lower than seem consistent with the energetic requirements of long-range flight. Extrapolations of the possible flight paths of such birds (Figs. 8-10) suggested that birds, even some of those flying at the higher speeds, may take several days in attempting to cross the Western North Atlantic. 4. Birds appeared to fly at higher altitudes during the day than at night, perhaps to allow temperature regulation without evaporative water loss. 5. The results are discussed in relation to previous laboratory measurements of caloric expenditures and flight speeds of birds in wind tunnels, possible use of structure in the atmosphere by small migrants, and the selection pressures which might play a role in the phenomenon of long migrations over water. [ABSTRACT FROM AUTHOR]

The article discusses the predation attempts by short-eared owl (Asio flammeus) and long-eared owls (Asio otus) on migrating songbirds that are attracted to artificial lights. It claims that the two owl species are distributed in North America, Europe, the Middle East and Asia. The species mostly eat small mammals, as well as birds, reptiles, and amphibians.

In this article, the author discusses the relationship of broodedness and latitude and how these factors affect the responsiveness of female birds to supplemental food. The author is critical of the explanations of the observed patterns, primarily because of errant broodedness assignments for a number of species. The notes on broodedness in "The Birds of North America" are also discussed.

A correction to an article on North American landbird vagrancy published in a previous issue is presented.

The article provides information on the characteristics of the blue jay, a common bird in the eastern North America. This bird is known to eat insects which are injurious to forest trees. It also steals fruits or other birds' eggs, and even kills young birds in the nest. The bird migrates to the country during winter seasons.