ADAPTATIONS TO CLIFF‐NESTING IN SOME ARCTIC GULLS ( LARUS)

• Published in: Ibis
• Main Author: Smith, Neal G.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1966
• Subjects: Arctic; rissa tridactyla
• Online Access: http://dx.doi.org/10.1111/j.1474-919x.1966.tb07252.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1474-919X.1966.tb07252.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1474-919X.1966.tb07252.x

SUMMARY Various aspects of the breeding of three gulls, Larus thayeri, glaucoides and hyperboreus , which nested in colonies both on cliff ledges and on level ground in the eastern Canadian Arctic, were compared with those of the ground‐nesting L. argentatus and the cliff‐nesting Rissa tridactyla . As the result of adaptation to cliff ledge nesting, many aspects of the breeding biology of R. tridactyla were strikingly different from those of the ground‐nesting European L. argentatus , but the behaviour of L. thayeri, glaucoides and hyperboreus clearly spanned these differences. Cliff‐nesting individuals of thayeri and glaucoides were most like Rissa ground‐nesting individuals of these species were most like argentatus. L. thayeri was more like Rissa than was glaucoides . With but few exceptions, both cliff‐ and ground‐nesting individuals of hyperboreus were most like argentatus . The factors responsible for the intra‐specific differences between cliff‐ and ground‐nesters of thayeri and glaucoides are not clear. Limited gene exchange between cliff and ground colonies occurs. Because of physical features of the nest, first‐laid eggs were more liable to fall from ledges than second or third eggs. L. thayeri and glaucoides have evolved separate mechanisms to cope with this problem. Egg shape was multimodal in thayeri and glaucoides . Long pyriform eggs were less liable to fall from ledges than eggs of other shapes. L. thayeri laid more long pyriform eggs as first eggs than did glaucoides. L. thayeri lost fewer eggs than did glaucoides , but glaucoides replaced all lost eggs while thayeri did not. Delayed follicular atresia provided glaucoides with insurance of egg replacement. In thayeri , accessory follicles were reabsorbed after the first egg was laid; in argentatus , after the second egg, and in glaucoides after the third egg. At the approach of a predator, it was advantageous for cliff‐dwelling chicks to remain motionless but for ground‐dwelling chicks to flee their nests and to hide. Among the cliff‐nesters, ...