THE BEHAVIOUR OF BIRDS IN CONTINUOUS DAYLIGHT

• Published in: Ibis
• Main Author: Armstrong, Edward A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1954
• Subjects: Arctic; Lapland
• Online Access: http://dx.doi.org/10.1111/j.1474-919x.1954.tb04108.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1474-919X.1954.tb04108.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1474-919X.1954.tb04108.x

Summary. The Strigiformes and Charadriiformes tend to be more persistently active in continuous daylight than the Falconiformes. In Lapland at midsummer passerine song reaches a minimum a few hours before midnight and a maximum in the hours immediately following midnight. The song‐lull cannot be equated with the quiescent period. The quiescent period of three species, studied at the nest, the Willow Tit, Fieldfare and Dipper, occurs at different times. There is evidence that the nestling period of some passerines is shorter in the arctic than in lower latitudes‐suggesting, ceteris paribus , an inverse relationship between length of the nestling period and length of daylight. Light appears to be the dominant external factor governing bird activity in the arctic. The coloration of many species is correlated with the extent to which they are active in dim light. The continuous daylight of the arctic summer accentuates the adaptive value of cryptic coloration to open‐nesting birds vulnerable to predatory birds.