Time of Day Effect on the Foraging Behaviour and Hunting Success of the Great Grey Shrike Lanius excubitor During the Non-Breeding Period

The allocation of time and energy for foraging relative to other activities is a critical topic in behavioural ecology. Optimal foraging theory has been extensively studied in ‘active foraging’ species, whereas ‘energy maximizers’ employing a sit-and-wait feeding strategy have been less frequently researched. From 2014 to 2018, we investigated the hunting and feeding behaviour of the Great Grey Shrike Lanius excubitor, a species with a sit-and-wait hunting strategy, during the non-breeding period in eastern Poland. Birds in this region must cope with low temperatures, snow cover that reduces prey accessibility, and short daylight hours that restrict foraging time. Our findings show that foraging and hunting behaviours comprised 93% of the observation time. Shrikes spent the most time feeding in the morning and the least in the evening, with an average catch success rate of 19.8%. Hunting success was unaffected by weather conditions, seasonal progression, and time of day. Shrikes are known to create larders, which they use to store prey for later consumption. On average, the birds required 2.4 visits to their larder to consume rodent prey, most frequently at dawn (58.3% of 24 recorded attempts). Our calculations indicate that on average, a single shrike captured an estimated 450 vertebrates and 634 invertebrates from October through March. This study highlights the importance of the Great Grey Shrike’s hunting strategies and adaptive behaviours associated with time of day, which are crucial for their survival during the non-breeding season, including winter. With increasingly mild winters, the key factor determining the population size of this species will likely be the food resources in their habitats.