Meeting Abstract

P3.77  Monday, Jan. 6 15:30  Triglycerides as markers of fattening rate in non-migratory passerines: effects of ambient temperature DEVOST, I; HALLOT, F; MILBERGUE, M; PETIT, M; VEZINA, F*; Univ. Quebec, Rimouski ; Univ. Quebec, Rimouski ; Univ. Quebec, Rimouski ; Univ. Quebec, Rimouski ; Univ. Quebec, Rimouski francois_vezina@uqar.ca

In migratory birds, levels of blood triglyceride (TRIG) have been repeatedly shown to correlate with the rate of fat accumulation during stopover. Since fattening rate can be estimated from a single capture, this makes this marker a valuable tool for studying constraints on rate of migration. Similarly to birds fattening for migration, small non-migratory passerines wintering at northern latitudes also become hyperphagic during winter. They must accumulate fat on a daily basis to survive through the night fasts. The use of TRIG to infer fattening rate from single captures could therefore be used in the field as a tool to monitor individual performance in energy acquisition. However, daily fattening rate is likely to be affected by seasonal changes in ambient temperature, as the need for energy reserves will change with thermoregulation costs. Using captive black-capped chickadees (Poecile atricapillus) as our model species, we conducted an experiment to (1) validate the use of TRIG as a predictor of fattening rate in resident birds and (2) determine the effect of ambient temperature on the relationship between TRIG and fattening rate. We first measured daily mass gain and sampled blood for TRIG in birds maintained at 15°C. Then, birds were separated in two groups, one maintained at 0°C and the other maintained at 30°C (thermoneutrality) before repeating the sampling. As expected, we found significant positive correlations between daily fattening rate and plasma TRIG levels. However this effect was dependent on ambient temperature with the strongest relationship found at 0°C and a lack of correlation at thermoneutrality.