Body composition and flight ranges of Bar-tailed Godwits (Limosa lapponica baueri) from New Zealand

Body composition analysis was performed on 37 Bar-tailed Godwits (Limosa lapponica baueri) that had been illegally shot during migratory fueling in northern New Zealand in March 1992. Adults (n = 35) were heavy (442-721 g), with fat loads of 30-45% of body mass. Two first-year males had only 5.4% and 8.9% fat, respectively, and had 13% less lean (fat-free dry) tissue than the average adult male. Males and females scaled along the same size axes, with little overlap between the sexes (females were larger). Larger birds carried more fat, but fat loads did not cliff er systematically with size (and, therefore, sex). Fatter birds (after accounting for body size) had larger flight muscle and lung masses, implying premigratory hypertrophy. Males that were not in body molt were fatter, but less colorful, than molting birds. They were also longer-winged and had larger testes but smaller intestines and salt glands, which suggests that they may belong to a subpopulation with a different fueling and molt strategy. Comparison between L. l. baueri and a smaller subspecies (L. l. taymyrensis) indicated that although the two subspecies scaled along the same lean mass-size axes, L. 1. baueri deposited much more fat for their body size (1.7x more than the equivalent-sized L. 1. taymyrensis). On the basis of estimated travel costs for L. 1. taymyrensis, predicted flight ranges for L. 1. baueri ranged from 6,000 to 8,600 km, depending on whether wind assistance is assumed. That suggests that direct flights from New Zealand to southeastern or eastern Asia are possible (e.g. Philippines, 7,200 km; Japan, 8,700; South Korea, 9,100 km).