Latitudinal variation in blue tit and great tit nest characteristics indicates environmental adjustment

Aim The laying of eggs and the building of a nest structure to accommodate them are two of the defining characteristics of members of the class Aves. Nest structures vary considerably across avian taxa and for many species the structure of the completed nest can have important consequences both for parents and their offspring. While nest characteristics are expected to vary adaptively in response to environmental conditions, large‐scale spatial variation in nest characteristics has been largely overlooked. Here, we examine the effects of latitudinal variation in spring temperatures on nest characteristics, including insulatory properties, and reproductive success of blue tits, Cyanistes caeruleus, and great tits, Parus major. Location Great Britain. Methods Nests and reproductive data were collected from seven study sites, spread over 5° of latitude. The nest insulatory properties were then determined before the nests were separated into nest base material and cup lining material. Results As spring temperatures increased with decreasing latitude, the mass of the nest base material did not vary in either species, while the mass of the cup lining material and nest insulatory properties decreased in both species. This suggests that in response to increasing temperatures the breeding female reduces the mass of the cup lining material, thereby maintaining an appropriate microclimate for incubating and brooding. The mean first egg date of both species advanced with decreasing latitude and increasing spring temperatures, although clutch size and brood size at hatching and fledging did not vary. Main conclusions This is the first study to demonstrate that the nest‐construction behaviour of birds varies in response to large‐scale spatial variation in ambient temperatures. Therefore, nest composition reliably indicates environmental conditions and we suggest that studies of nest structure may be sentinels for the early signs of rapid climate change.     

Leukotriene C4 and D4 formation by particulate enzymes

The homogenate of rat basophilic leukemia cells, when incubated with arachidonic acid, glutathione, and calcium, formed 3 isomers of 5,12-dihydroxyeicosatetraenoic acid and 2 isomers of 5,6-dihydroxyeicosatetraenoic acid, as well as leukotriene (LT) C4 and D4. The products were identified by high pressure liquid chromatography, ultraviolet spectral analysis, co-migration with standards, bioassay, and gas chromatography-mass spectrometry. The enzymes responsible for the formation of LTC4 and LTD4 from LTA4 were found in the 10,000 x g pellet and, therefore, appear to be particulate. The possibility that these enzymes are bound to the cell membrane suggest that the formation of these leukotrienes might be important in the basophil and mast cells release reaction.