Redpath Steve, Thompson Alex, Amar Arjun
Institute of Biological and Environmental Science, Aberdeen University, Zoology Building, Tillydrone Av, Aberdeen, AB24 2TZ, UK.
FitzPatrick Institute of African Ornithology, DST/NRF Centre of Excellence, University of Cape Town, Rondebosch, 7701, South Africa.
BMC Evol Biol. 2017 Jun 19;17(1):144. doi: 10.1186/s12862-017-0986-z.
Most birds exhibit bi-parental care with both sexes providing food for their young. Nestling signal food needs through begging. However, for some species, males rarely visit the nest, so have limited opportunity for gaining information directly from the chicks. Instead, females beg when males deliver food. We tested whether this calling signalled nutritional need and specifically the needs of the female (Breeder Need hypothesis) or that of their chicks (Offspring Need hypothesis).
We observed begging and provisioning rates at 42 nests of hen harrier (Circus cyaneus) in Scotland, explored the factors associated with variation in begging rate and the relationship between begging and provisioning. We also tested the impact of food on begging and provisioning through a feeding experiment. Female begging rate increased up to a chick age of 3 weeks and then tailed off. In addition, begging increased when broods were large.
Our data provided support for the Offspring Need hypothesis. At nests where adlib food was provided females reduced their begging rate. These patterns suggested that female begging was an honest signal of need. However, begging continued even with adlib food and was only weakly associated with greater provisioning by males, suggesting that these calls may also play an additional role, possibly reflecting sexual or parent-offspring conflict.
大多数鸟类表现出双亲育雏行为，两性都会为雏鸟提供食物。雏鸟通过乞食来表明食物需求。然而，对于一些物种来说，雄性很少光顾巢穴，因此直接从雏鸟那里获取信息的机会有限。相反，当雄性提供食物时，雌性会发出乞食信号。我们测试了这种叫声是否表明了营养需求，特别是雌性的需求（繁殖者需求假说）还是雏鸟的需求（后代需求假说）。
我们观察了苏格兰42个矛隼（Circus cyaneus）巢穴的乞食率和喂食率，探究了与乞食率变化相关的因素以及乞食与喂食之间的关系。我们还通过喂食实验测试了食物对乞食和喂食的影响。雌性的乞食率在雏鸟3周龄前上升，之后逐渐下降。此外，当雏鸟数量较多时，乞食行为会增加。
我们的数据为后代需求假说提供了支持。在提供充足食物的巢穴中，雌性降低了它们的乞食率。这些模式表明雌性的乞食是需求的诚实信号。然而，即使有充足的食物，乞食行为仍会持续，并且与雄性更多的喂食行为之间的关联较弱，这表明这些叫声可能还起到了额外的作用，可能反映了性别冲突或亲子冲突。
