Black-capped Chickadees Parus Atricapillus Research Articles

Differences in Breeding Bird Assemblages Related to Reed Canary Grass Cover and Forest Structure on the Upper Mississippi River

Abstract Floodplain forest of the Upper Mississippi River provides habitat for an abundant and diverse breeding bird community. However, reed canary grass Phalaris arundinacea invasion is a serious threat to the future condition of this forest. Reed canary grass is a well-known aggressive invader of wetland systems in the northern tier states of the conterminous United States. Aided by altered flow regimes and nutrient inputs from agriculture, reed canary grass has formed dense stands in canopy gaps and forest edges, retarding tree regeneration. We sampled vegetation and breeding birds in Upper Mississippi River floodplain forest edge and interior areas to 1) measure reed canary grass cover and 2) evaluate whether the breeding bird assemblage responded to differences in reed canary grass cover. Reed canary grass was found far into forest interiors, and its cover was similar between interior and edge sites. Bird assemblages differed between areas with more or less reed canary grass cover (>53% cover breakpoint). Common yellowthroat Geothlypis trichas, black-capped chickadee Parus atricapillus, and rose-breasted grosbeak Pheucticus ludovicianus were more common and American redstart Setophaga ruticilla, great crested flycatcher Myiarchus crinitus, and Baltimore oriole Icterus galbula were less common in sites with more reed canary grass cover. Bird diversity and abundance were similar between sites with different reed canary grass cover. A stronger divergence in bird assemblages was associated with ground cover <15%, resulting from prolonged spring flooding. These sites hosted more prothonotary warbler Protonotaria citrea, but they had reduced bird abundance and diversity compared to other sites. Our results indicate that frequently flooded sites may be important for prothonotary warblers and that bird assemblages shift in response to reed canary grass invasion.

Impact of an ice storm on resident bird populations in eastern North America

The January 1998 ice storm was very dramatic, particularly in Québec, with five days of nearly non-stop freezing rain and temperatures below 0 °C. We compared results of Christmas Bird Counts (complete counts conducted during one day within a 12-km radius by volunteers in winter) conducted before (1997–1998) and after (1999) the storm in control areas (16 sites) and in affected areas (15 sites). Abundance ratios (after/before) were significantly higher in control versus affected sites for Rock Dove Columba livia, Mourning Dove Zenaida macroura, Hairy Woodpecker Picoides villosus, Blue Jay Cyanocitta cristata, Black-Capped Chickadee Parus atricapillus and House Sparrow Passer domesticus. Paired -t- tests also indicated that the abundance of Brown Creeper Certhia americana and Downy Woodpecker Picoides pubescens was lower in affected sites following the storm. Only European Starling Sturnus vulgaris abundance increased significantly in affected sites. Species found in open habitats that forage mostly on the ground were less affected by the storm than tree foragers were. The effect of the storm on bird populations was quite significant and increased frequency of such storms could have drastic consequences on bird populations in the long term. Key words: ice storm, birds, Christmas Bird Counts, winter survival, climate change

Cache Pilfering and Its Prevention in Pairs of Black-Capped Chickadees

Black-capped Chickadees Parus atricapillus scatter hoard food. Because they live in social groups during the winter, flock members may observe caching by others and take their caches. We present two laboratory experiments that investigate the possibility of observational learning of cache location and related behaviours. In the first experiment, 15 chickadees were observed storing food in an indoor aviary, either individually or in pairs. Five percent of caches were taken within a few minutes by birds that observed the occurrence of caching. These cache thefts may have been assisted by observation. Dominant birds made more caches and subordinate birds were more likely to take another bird's caches. When cache recovery was tested several hours later, birds recovered their own caches more accurately than those of other birds but recovery of other birds' caches was not improved by the previous observation of caching. A second experiment with 6 additional chickadees examined whether birds attempt to conceal their caching activity. In this experiment 9% of caches were taken by birds that had the opportunity to observe caching. When birds carried seeds, they flew away from their companion more than they did when they were flying without a seed. Overall, these results are consistent with those of previous laboratory studies and suggest that conspecific cache theft may be relatively rare in flocks of food-storing chickadees.

Social Dominance, Food Caching and Recovery by Black-Capped Chickadees Parus atricapillus: Is There a Cheater Strategy?

Social Dominance, Food Caching and Recovery by Black-Capped Chickadees Parus atricapillus: Is There a Cheater Strategy?

Winter territoriality and flock cohesion in the black-capped chickadee Parus atricapillus

In northwest Massachusetts, black-capped chickadees shifted foraging groups repeatedly each day during the winter. As a result, there was no clear distinction between flock members and floaters, but instead a continuous gradation from birds that formed relatively stable associations to those that shifted groups more frequently. Group territories were absent and individual territories were at most poorly defended, if present at all. This picture differs from other recently studied populations, where flock membership is stable and flock territories are clear. Comparison with other populations indicates that winter social structure in the black-capped chickadee may be sensitive to both winter food levels and the proportion of year-round residents. This indicates that cost-benefit analyses of winter social organization should consider factors acting throughout the year as well as the residence status of the wintering birds. The data suggest that flock size, population density and home range size are sensitive to winter food on the study area, whereas territoriality and flock cohesion may respond more clearly to the local availability of breeding resources or the proportion of year-round residents.

Nocturnal hypothermia and its energetic significance for small birds living in the arctic and subarctic regions. A review

Nocturnal hypothermia is demonstrated in a number of small northern birds. These birds utilize hypothermia among other energy-saving mechanisms and lower the body temperature by some 10°C. In most bird species hypothermia is utilized only in conjunction with a state of inanition. However, hypothermia has also been demonstrated in birds with satisfactory feeding conditions and body weight. For none of the small northern birds utilizing nocturnal hypothermia. is inanition necessary for the induction of a state of hypothermia. A seasonal effect on the hypothermic response has been demonstrated for two species of tits, the black-capped chickadee Parus atricapillus and the willow tit Parus monfanus, and also for an Andean hummingbird. The depth of hypothermia achieved significantly and linearly was correlated with the ambient temperature for the same two species of tits. By the use of nocturnal hypothermia, birds living in temperate zones can save as much as 75% of their energetic costs, compared with their energy consumption at normal body temperature. The reduction in the nightly expenditure of energy is considerable also in small-sized arctic and subarctic birds that utilize nocturnal hypothermia. The saving of energetic costs may easily represent the margin between life and death for such small birds living under the combined stresses of hunger, cold and long nights.

Metabolic Rate and Temperature Regulation of Winter Acclimatized Black-Capped Chickadees Parus atricapillus of Interior Alaska

Metabolic Rate and Temperature Regulation of Winter Acclimatized Black-Capped Chickadees Parus atricapillus of Interior Alaska