Effects of Climate and Nutrition on Growth and Survival of Willow Ptarmigan Chicks

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Abstract
Effects of ambient temperature (Ta), and food availability and quality on growth and survival of Willow Ptarmigan chicks Lagopus l. lagopus were investigated in the laboratory. Under standard food conditions, growth increased with increasing Ta. Onlya persisting sub-zero Ta affected survival. Because of changes in the chicks'' behaviour a 67% reduction of food availability did not affect their growth and survival. When food was available only 22% of the time, however, all chicks died within 5 d after hatching, irrespective of Ta. Even small reductions in food quality strongly affected growth and survival. Food intake was always correlated with body weight, irrespective of age, Ta, and food quality. These results indicate that young ptarmigan chicks are unable to compensate for increased energy expenditure and reduced food quality with increased food intake. Therefore the availability of high quality food seems to be crucial for their growth and survival, while low ambient temperatures per se seem to be of little consequence.