Effect of variation in nestling hunger levels on the begging behavior of nestlings and the provisioning behavior of adult American Kestrels

Little is known about how variation in nestling begging affects the behavior of adult raptors and how responses of adult males and females might differ. Our objective was to manipulate the begging intensity of nestling American Kestrels (Falco sparverius) to examine the responses of adult males and females. We studied 12 pairs of kestrels and their broods from 1 May – 1 July 2014 in Madison County, Kentucky. To manipulate hunger levels, nestlings were fed until satiated and deprived of food. The begging behavior of 12-26-day-old nestlings and provisioning behavior of adults were video-recorded prior to (control) and after treatments. Proportion of nestlings begging did not differ at adult arrival, but differed at adult departure (F2,19 = 13.79, p = 0.0002). Intensity of begging differed at both arrival (F2,19 = 9.93, p = 0.0011) and departure (F2,19 = 15.96, p \u3c 0.0001), and nestling vocalizations in absence of a parent differed among treatments (F2,19 = 5.87, p = 0.0104). In response to treatments, adults increased and decreased their provisioning rates (F2,19 = 10.36, p = 0.0009). Adults visited food-deprived nestlings (4.164 visits/nestling/hour) four times the rate for nestlings that were fed to satiation (1.068 visits/nestling/hour). Adult males and females provisioned at similar rates (F1,57 = 2.770, p = 0.1014). The begging behavior of nestling American Kestrels varies with hunger level and is an honest signal of need. Adult kestrels interpret begging signals and respond by modifying their provisioning rates, and male and female kestrels respond to nestling signals in similar ways

Effect of Variation in Nestling Hunger Levels on the Begging Behaviour of Nestlings and the Provisioning Behaviour of Adult American Kestrels

Little is known about how variation in nestling begging intensity influences the behaviour of adult raptors and how responses of adult males and females to such variation might differ. Our objective was to manipulate the begging intensity of nestling American Kestrels (Falco sparverius) and examine the responses of adults. We studied 12 pairs of American Kestrels nesting in nest boxes from 1 March to 1 July 2014 at the Blue Grass Army Depot, Madison County, Kentucky. Nest boxes were modified with a separate compartment for a camcorder to record nestling behaviour, and a second camcorder was placed outside the nests to monitor adult behaviour. To manipulate nestling hunger levels, 12 to 26-day-old nestlings in six nests were deprived of food for 24 h and those in the other six nests were fed until satiated. At each nest, we alternated control (no treatment) and treatment (fed or food deprived) days over a 4 day period to minimise the possible effect of nestling age on adult and nestling behaviour. Nestling begging intensity differed among treatments, with nestlings in food-deprived nests begging with greater intensity after food deprivation and those in fed-treatment nests begging with less intensity after being fed. Adult male and female American Kestrels provisioned nestlings at similar rates, with both sexes feeding nestlings at higher rates after food deprivation and at lower rates after fed treatments. Thus, the begging behaviour of nestling American Kestrels varied with hunger level, and adult American Kestrels responded by adjusting provisioning rates. Although the response of adults to nestling begging suggests that natural selection might favour \u27dishonest\u27 begging to obtain more food, the potential costs of \u27dishonest\u27 begging, such as attracting predators, reduced immunocompetence, and loss of indirect fitness benefits if such begging negatively impacts siblings and parents, may outweigh any possible benefit

Effect of Variation in Nestling Hunger Levels on the Begging Behaviour of Nestlings and the Provisioning Behaviour of Adult American Kestrels

Little is known about how variation in nestling begging intensity influences the behaviour of adult raptors and how responses of adult males and females to such variation might differ. Our objective was to manipulate the begging intensity of nestling American Kestrels (Falco sparverius) and examine the responses of adults. We studied 12 pairs of American Kestrels nesting in nest boxes from 1 March to 1 July 2014 at the Blue Grass Army Depot, Madison County, Kentucky. Nest boxes were modified with a separate compartment for a camcorder to record nestling behaviour, and a second camcorder was placed outside the nests to monitor adult behaviour. To manipulate nestling hunger levels, 12 to 26-day-old nestlings in six nests were deprived of food for 24 h and those in the other six nests were fed until satiated. At each nest, we alternated control (no treatment) and treatment (fed or food deprived) days over a 4 day period to minimise the possible effect of nestling age on adult and nestling behaviour. Nestling begging intensity differed among treatments, with nestlings in food-deprived nests begging with greater intensity after food deprivation and those in fed-treatment nests begging with less intensity after being fed. Adult male and female American Kestrels provisioned nestlings at similar rates, with both sexes feeding nestlings at higher rates after food deprivation and at lower rates after fed treatments. Thus, the begging behaviour of nestling American Kestrels varied with hunger level, and adult American Kestrels responded by adjusting provisioning rates. Although the response of adults to nestling begging suggests that natural selection might favour \u27dishonest\u27 begging to obtain more food, the potential costs of \u27dishonest\u27 begging, such as attracting predators, reduced immunocompetence, and loss of indirect fitness benefits if such begging negatively impacts siblings and parents, may outweigh any possible benefit