Experiences in the first days and weeks of life can have a profound impact on humans — and birds.
By following more than 100 puppies from barn swallow (A rustic swallow) during their first two weeks of life, scientists demonstrated that the puppies’ growth was harmed by cold periods if these occurred in the five days following hatching, if they were smaller siblings and if the parents brought less food to the nest.
According to , the hot weather also delayed the growth of the chicks, both at the beginning and at the end of development, and the parents were unable to protect the chicks against the heat by feeding them more.
In a new one, published last month in PLOS Onethe team monitored the development of 113 puppies of barn swallows from 31 nests, from before hatching until the chicks were about 13 days old.
To continuously monitor the local temperature, the researchers placed thermometers around 30 centimeters of each nest. They also investigated whether family dynamics, the size of a chick in relation to its siblings and the frequency with which parents bring food to the nest, aggravate or alleviate heat stress.
Like mammals, birds can regulate their body temperature, but only a few days after hatching.
“Birds are simultaneously ectotherms and endotherms throughout the same lifetime. It is not just about developing thermal insulation, but also about the development of physiological heating and cooling mechanisms about a week after hatching”, explained the first author of the study, Sage Madden.
The results revealed that barn swallow chicks are sensitive to extremely low temperatures, high temperatures, and temperature fluctuations.
Lower minimum temperatures have been associated with a growth delaybut only if the chicks were exposed to these cold spells within the first five days after hatching.
This negative effect was aggravated in nestlings whose parents provided them with less food and in the smallest nestling in each nest.
In contrast, all puppies were negatively affected both due to high maximum temperatures and temperature variability, regardless of their age during the heat wave or how often their parents fed them.
“Our study provides a picture of how different aspects of the thermal environment affect nestling growth and how social factors can protect these birds from human-induced environmental changes,” concluded Madden.
