JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. University of California Press and CooperOrnithological Society are collaborating with JSTOR to digitize, preserve and extend access to The Condor.ABSTRACT. -Oxygen consumption was measured in order to estimate basal metabolic rate in a variety of Malaysian birds. Oxygen consumption during the active phase of the circadian cycle was greater than during the resting phase. Oxygen consumption was lower than that of temperate species of the same weight by 30% during the active phase and 35% during the resting phase. Species that forage in the sun seemed to consume less oxygen than those that forage in the shade.The baseline for many studies of comparative avian metabolism is provided by the basal metabolic rate (Hb); the rate of energy turnover that occurs in the thermoneutral zone of resting, post-absorptive animals. Various factors have been shown to have a systematic influence upon Hb in birds (for recent reviews see Aschoffand Pohl 1970b, Calder and King 1974, Kendeigh et al. 1977). In deriving predictive equations for some of these relationships however, the effect of climate has been largely ignored (King and Farner 1961, Lasiewski and Dawson 1967, Aschoff and Pohl 1970a, b). An early review by Scholander et al. (1950) concluded that climate had no influence upon energy metabolism although later evidence proved contrary (Enger 1957, Hart 1957, Hudson and Kimzey 1966, Kendeigh and Blem 1974). Desert species and subspecies have been shown to have lower metabolic rates than those from more mesic climates (Trost 1972, Dawson and Bennet 1973). Kendeigh et al. (1977) showed that the widely used equations of Aschoff and Pohl (1970a) are not always applicable if summer or winter temperature adaptation occurs, and gave some indication of latitudinal differences in avian metabolism. In a re-examination of the literature, Weathers (1979) showed that Hb for a variety of species could vary from 50-100% of values predicted by the Aschoff and Pohl (1970a) equations, depending upon the latitude of origin. This being the case, current predictive equations have limited use outside temperate regions.Since data from tropical birds are few, and often conflicting, the aim of this study was to make further measurements, which would allow prediction of Hb for energetics studies in the tropics. (307'N, 101042'E). All the insectivores, and most of the other species were measured on the day of capture. Occasionally some of the bulbuls, estrildids and finches were maintained in an outdoor aviary and given unlimited fruit and seed; the period of captivity did not exceed 48 h for a bulbul or five days for the others. Captive birds were the same weight as freshly caught specimens. The birds were netted betwe...

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Energy budgets and growth data are presented for nestlings of three species of tropical insectivores: White-bellied Swiftlets (Collocalia esculenta), Blue-throated Bee-eaters (Merops viridis), and Pacific Swallows (Hirundo tahitica). A comparison with temperate nestlings, matched for body size, shows that the peak energy demand in our tropical sample averaged around 60% of temperate counterparts. We attribute savings to slow growth rates, reduced thermoregulatory requirements, a low resting metabolism (in swallows only), asynchronous hatching (in bee-eaters), and low nestling activity levels. Patterns of energy storage as lipid in nestlings of the three species were similar to the pattern in temperate swallows (Hirundinidae) and swifts (Apodidae), with those species feeding at the greatest heights, and hence on the most unpredictable supplies, storing the most fat while in the nest.

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The influence of nest harvesting upon nest construction and egg‐laying was studied in the White‐nest Swiftlet Aerodramus fuciphagus and the Black‐nest Swiftlet A. maximus in Singapore. A study of nestling energetics allowed an estimate to be made of adult foraging abilities. The energy and nutrients required for nest construction are easily acquired by foraging but the females may face a shortage of energy or depletion of stored lipids during egg formation. Removal of nests did not affect the size or quality of replacement nests or clutches, but may aggravate the lipid shortage. Nest removal did reduce breeding success in replacement nests and, in the White‐nest Swiftlet, disturbance to the colony resulted in an increased laying interval between first and second eggs. Our results indicated that commercially exploited colonies should be left unharvested for the middle part of the breeding season to allow a period of successful reproduction.