Variation in allocation of time, water and energy in Hoopoe Larks from the Arabian Desert

1. Patterns of resource allocation in different times of the year can provide insights into the effects of simultaneous environmental constraints on reproduction and survival of desert birds. Field metabolic rate (FMR), water influx rate (WIR) and patterns of time allocation of Hoopoe Larks ( Alaemon alaudipes Desfontaines) were investigated during spring, when larks were rearing offspring, and during summer, presumably the harshest time for desert birds, in the Arabian Desert. 2. FMR was 45% below allometric predictions in spring (1·83 times basal metabolic rate, BMR) and 58% below predictions in summer (1·37 times BMR). WIR was 37% lower than predicted during the nestling period and 55% lower than predicted during summer. 3. Activity patterns during spring and summer were bimodal, with birds foraging in the early morning and late afternoon and resting in the shade or attending the nest during midday. Foraging time was similar in spring (32·0% of total daytime) and summer (33·6% of total daytime), despite higher energy and water intakes for parents and offspring in spring, suggesting that food availability was higher in spring. The nonforaging time was entirely spent resting in summer, while in spring half of this time was allocated to caring for offspring and the other half to resting in the shade. Hoopoe Larks fed their offspring 55 times per day and shaded their chicks about 5 h per day to protect them from solar radiation. 4. High T a s combined with low and unpredictable food availability in deserts may constrain reproduction by limiting the amount of time, water and energy that parents can devote to rearing offspring.