Seasonal Variation in Pigeon Body Weight and Delayed Matching-to-sample Performance

The weights of 5 pigeons with free access to food, monitored over 3 calendar years in the laboratory, were found to fluctuate with season. All pigeons were at their heaviest in the winter and were lightest in the summer. Five different pigeons performed a standard delayed matching-to-sample task for 44 weeks from January to November. Their weights were held at 85% of their summer free-feeding weights, making their predicted deprivation level higher in the winter relative to predicted winter free-feeding weights. Slopes of forgetting functions fit to weekly response totals for each pigeon were shallower in winter, showing an improvement in accuracy with longer delays. Thus, delayed matching-to-sample performance may have been affected by the practice of maintaining the pigeons at a constant body weight throughout the calendar year

The potential for comparative research across New World bird migration systems

For a migratory bird, the costs and benefits of utilizing a given migratory strategy vary according to the biotic (e. g., physiology) and abiotic (e. g., weather) constraints it experiences throughout the year. In the New World, closely related species migrate to breeding grounds located across a wide range of latitudes, from northern North America to southern South America. Because the ultimate goal of a bird on spring migration is to successfully arrive on the breeding grounds in a timely manner, events that occur during the breeding season (e. g., amount of time available to breed) could affect, through selection pressures, the behavior of birds on spring migration. Variation across north temperate, tropical, and south temperate latitudes in breeding strategies, breeding season length, and availability of food during the breeding season has been well documented in various bird species. Thus, such factors as migratory strategies, risk of mortality on migration, and effects of climate change on migratory patterns may also vary predictably, depending on the latitude, both north and south of the Equator, at which a migratory population breeds. Comparing such patterns across the New World, using interdisciplinary approaches and the latest in technological advances, holds promise for better understanding how migratory birds accomplish these spectacular journeys.Fil: Jahn, Alex. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; ArgentinaFil: Cueto, Víctor. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentin

Data from: Do migratory and resident birds differ in their responses to interacting effects of climate, weather and vegetation?

Aim: Knowledge of the individual and collective effects of habitat, weather variability, and climate on bird populations is limited, with the result that species vulnerability to the collective impacts of global change is poorly understood. We quantified the effects of interactions between these potential drivers on the occurrence of resident, migratory, and nomadic birds in Australian temperate woodlands. Location: A 1.8 million hectare temperate woodland belt in south-eastern Australia. Time period: 2002-2015. Major taxa studied: Temperate woodland birds. Methods: We used logistic mixed models to quantify the factors affecting the occurrence of three groups of birds (residents, partial migrants, nomads) at 203 long-term field sites located in three vegetation types (restoration plantings, natural regrowth woodland, old growth woodland) surveyed repeatedly between 2002 and 2015. Potential explanatory variables included vegetation type, three long-term climate variables (mean annual rainfall, maximum temperature, minimum temperature), and the three corresponding weather variables for 12 months preceding each survey. Results: We found four-way interactions between bird movement category, type of vegetation cover, and rainfall (both as a long-term climate variable and a short-term weather variable). Increased occurrence of nomads and partial migrants, but not resident species, was associated with high short-term rainfall. The effects were more marked in long-term climatically-wet areas, and also differed between vegetation types. Models for maximum and minimum temperature were simpler than those for rainfall, but showed evidence of partial migrants and nomadic species avoiding low minimum or high maximum temperatures in some vegetation types. Main conclusions: Our analyses revealed that birds with different movement patterns exhibit different responses to weather and long-term climate. Nomadic species in particular respond to rainfall strongly in climatically-wet locations (presumably because of large pulses in resources). Drying conditions resulting from climate change may therefore create problems for the future persistence of nomadic bird species