Nest complexity correlates with larger brain size but smaller body mass across bird species

Amniotes differ substantially in absolute and relative brain size after controlling for allometry,and numerous hypotheses have been proposed to explain brain size evolution.Brain size is thought to correlate with processing capacity and the brain’s ability to support complex manipulation such as nest-building skills.The increased complexity of nest structure is supposed to be a measure of an ability to manipulate nesting material into the required shape.The degree of nest-structure complexity is also supposed to be associated with body mass,partly because small species lose heat faster and delicate and insulated nests are more crucial for temperature control of eggs during incubation by small birds.Here,we conducted comparative analyses to test these hypotheses by investigating whether the complexity of species-typical nest structure can be explained by brain size and body mass(a covariate also to control for allometric effects on brain size)across 1353 bird species from 147 families.Consistent with these hypotheses,our results revealed that avian brain size increases as the complexity of the nest structure increases after controlling for a significant effect of body size,and also that a negative relationship exists between nest complexity and body mass.

The development of the Rook's(Corvus frugilegus)colony in the face of shifting spring phenology

Many birds species breed in colonies.One of the species in the Corvidae family nesting in groups is the Rook(Corvus frugilegus).The construction of the nest is costly for birds and needs high energy expenditure.Therefore,birds should optimize the time of nest building in relation to environmental,especially weather,conditions.Furthermore,birds should adapt their breeding phenology,including the date of starting the construction of nests for climate change.We observed the dynamics of increasing numbers of nests in a colony of Rooks in relation to air temperature,wind,rainfall,snowfall and day-length(indirect indicator of photoperiodism).Observations were carried out during three breeding seasons(2015-2017)in a large rookery in a big city in north-eastern Poland.The increase in the number of nests was correlated only with day length and no effect of climatic factors on the number of nests in the colony was observed.Number of nests varied significantly between successive years of research.In the case of the Rook(predictable breeders),the photoperiod seems to be the most important factor influencing breeding behavior,especially nest construction.In the last three decades,increasing temperature and time of spring phases have advanced and have influenced changes in the phenology of the availability of food resources.Simultaneously,a rapid decline in the numbers of breeding pairs of the Rook in Poland has been observed,especially in the last three decades.Conservative attachment to the length of the day,which is the main factor responsible for the development of the breeding colony,makes the Rook appear to be a species with low plasticity in the face of rapid climate changes.Thus,we suggest that may indirectly influence the decrease in the breeding population of the Rook.