A POPULATION STUDY OF SKYLARKS ALAUDA ARVENSIS

• Published in: Ibis
• Main Author: Delius, Juan D.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1965
• Subjects: Alauda arvensis
• Online Access: http://dx.doi.org/10.1111/j.1474-919x.1965.tb07332.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1474-919X.1965.tb07332.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1474-919X.1965.tb07332.x

SUMMARY A population of colour‐ringed Skylarks Alauda arvensis was studied intensely over two and less thoroughly over another five breeding seasons in Kavenglass, Cumberland. The breeding season extends from mid‐April to early July, but the onset, which is well synchronized, varies from year to year, probably depending on the spring temperature. One‐year‐olds lay the first clutch about a week later than older birds. Within a group of females there is a constancy in the laying order of first clutches from year to year. The rank of any given female seems to depend on an individual temperature threshold, which is reached four to seven days before laying, but other factors must play a role. The interval between the disappearance of a clutch or brood and the laying of the next clutch varies from four to six days depending on the stage at which the previous brood was lost. Beyond the 17th or 18th day of life the chicks of one brood no longer prevent the laying of a new clutch. No factors influencing the end of the season could be found. On average, Skylarks lay 2.7 clutches per year (range 1–5). Three successful broods seems to be the maximum. Average c/size is 3.69 eggs (range 3–5). The c/size varies with successive clutches, from 3.3 for first, to 4.0 for third clutches. Individual females tend to lay clutches of a characteristic size. No difference could be found between the clutches of one‐year and older birds, Females which retain the same territory from year to year show more consistency in clutch size than those which change territories. Data from different geographical locations in Europe suggest a cline from northwest to southeast of increasing clutch size. Clutch size does not seem to be affected by temperature. The variability of egg size and shape is discussed. 68% of the eggs laid hatched (incubation period 11 days) and 67% of the young hatched left the nest on the 8th day. About 90% of the eggs and young lost were taken by predators. No consistent seasonal differences in nest mortality could be found, ...