Egg size and laying date of long-billed curlews Numenius americanus: implications for female reproductive tactics

Call Number:

Keywords:

Abstract:

Annual differences in reproductive effort by female long-billed curlews (Numenius americanus) were clearly associated with changes in environmental conditions. During pre-laying in 1977 and 1978, long-billed curlews foraged almost exclusively on their breeding territories where vegetation height was generally short. Females did little flying prior to laying, and heavier females with relatively greater wing-disc loading laid larger egg and clutch volumes earlier in the season than did lighter females with lesser wing-disc loading. Tall, dense residual vegetation covered most upland breeding territories during pre-laying in 1979; and until grazing livestock broke down or removed this standing-dead vegetation, long-billed curlews regularly flew to undefended foraging sites on agricultural lands within 10 km of their territories. Nesting began significantly later in 1979 for all females, and lighter females not only laid earlier in the season, but they also laid larger eggs than heavier females. Path analyses indicated that body mass alone was a poor predictor of egg volume each year. Moreover, reduced egg volume was predicted by both high wing-disc loading and early laying only in 1979, suggesting that flight costs early in this season interfered with the ability of females to produce larger eggs. Reduced egg and clutch volumes by heavier females may have been a consequence of differential flight costs if these females were unable to accumulate sufficient reserves for larger eggs. More likely though, this reduced reproductive effort was a time saving and hence adaptive response to late nesting; further delay to produce larger eggs might have risked chick survival later in the season when conditions tend to deteriorate.

Notes:

Reference Code: A86RED02IDUS

Full Citation: Redmond, R. L. 1986. Egg size and laying date of long-billed curlews Numenius americanus: implications for female reproductive tactics. Oikos 46(3): 330-338.

Location: