Body Weights of Birds: a Review

Condor, 81: 193-202 0 The Cooper Ornithological Society 1979

BODY WEIGHTS OF BIRDS: A REVIEW

GEORGE A. CLARK, JR.

Although body weights are relevant to many particularly stressful flights, (3) failure to branches of avian biology, they have not been locate food in an unsuitable or unfamiliar recently reviewed. I here survey sources area, (4) failure to obtain enough food due an d uses for weight data, with reference to to social subordination (Rappole and Warner such variables as time of day, season, year, 1976), (5) reduction in weight that is adap- sex, migration, geography, climate, buoyancy, tive for prolonged stopovers, (6) loss of food size, and habitat. In addition, I consider opportunity to feed through time spent in uses of weights as standards for body size, in nets or being processed by banders, and (7) systematics, in assessing the physiological handling shock (Mueller and Berger 1966, condition of individuals, and in analyses of Leberman and Stern 1977). Determining the ecological communities. Excellent previous relative contribution of these factors in any reviews of this subject by Nice ( 1938), particular case can be difficult. Further Baldwin and Kendeigh ( 1938), Amadon attention should also be given to the possible ( 1943), Fisher ( 1955), Blake ( 1956), and occurrence of weight decreases due to Perrins (in Thomson 1964) do not cover many handling of nonmigratory birds (Rogers and recent discoveries and interpretations. Odum 1966). To avoid possible effects of handling, wild birds might in some cases be OBTAINING WEIGHTS weighed without capture by use of weighing perches (Moore 1953, Ellis and Varney 1974) Pettingill (1970:446), Bub (1967:61-63), and and uniquely marked with dye applied by Giles ( 1963 :4-5) outlined weighing tech- remote control. niques in which beam balances or small Ornithologists have assumed that a freshly spring scales are used (Berger 196S), with killed bird weighs the same as a live one, but live birds usually being confined in tubes or this may not be valid. Von Brijckel (1973) chambers for weighing. Records of age, sex, weighed 237 Garden Warblers (Sylvia horin) fat levels, time, locality, and other variables alive and 80 others within 15 min after death are useful in analyzing weights. Baldwin and and found that the dead birds averaged more Kendeigh ( 1938), Owen ( 1962)) and others than 1 g (5.5%) lighter. Possible differences have properly emphasized the need for large in weight between life and death need more samples of weights in comparing similar study. Under ordinary laboratory conditions populations. For some studies weights need dead birds gradually lose weight over a to be taken as uniformly as possible, e.g., period of hours by desiccation. However, sampling diurnally feeding species early in dead birds that are weighed, then frozen in the morning to minimize variation from daily sealed plastic bags, kept in humid conditions, weight cycles (Kontogiannis 1967). Breeding and later thawed and reweighed, lose rela- birds are best compared at known stages, tively little weight (2% or less) over a period because some species (e.g., certain penguins) of weeks (Grant 1965, Holmes 1976). vary greatly in weight through the breeding Researchers sometimes cannot directly cycle, and females of many species vary obtain weight data and therefore turn to the considerably during the period of egg laying. literature. Although weights have been After being banded, many, but not all, published for thousands of species, they are migratory birds lose weight for a day or two often difficult to find. Examples of publica- (Leberman and Stern 1977). This phenome- tions listing many North American weights non can, of course, be detected only in re- are Irving ( 1960), Hartman ( 1961)) and captured individuals who are ordinarily a Clench and Leberman (1978), but others are minority (commonly less than 20%) of the too numerous to mention. Brief summaries migrants initially captured. The cause of of weights should ideally include the sources weight declines in many recaptured migrants of data, the mean, standard deviation, range, is not well understood, and the reasons for and sample size for ten or preferably more the individual variations are unknown. Pos- adults of each sex in specified conditions, sible causes of the weight decreases include e.g., early in the day at a particular stage in ( 1) illness or other abnormalities, (2) re- the breeding season. Samples from represen- covery time for migrants that have completed tative geographic localities are also desirable. [1931 194 GEORGE A. CLARK, JR.

However, few published data meet these daily cycles in weight are less pronounced standards. Frequently samples are small, and (Irving 1960). Much remains to be learned weights have been obtained at varied, un- about effects of temperature and photoperiod specified times of day and at different times in influencing daily weight cycles and about of year. Data from different investigators are geographic and taxonomic differences in these often not comparable, for some specify age, cycles. sex, fat, migration status, and other variables, Seasonal and migratory. Weights are often whereas others do not. Moreover, sources high during winter in north temperate areas sometimes partially repeat data, e.g., one and during dry seasons in tropical regions reference including weights from another but (King 1972). A greater weight in winter of not clearly stating the nature of the duplica- many small, north temperate species reduces tion. Users of published weights should be the chance of starving to death in severe cautious, for pooling heterogeneous data from weather (Blem 1973, Calder 1974). In some the literature can be misleading. Alternatively, species, individuals are heavier during colder one might use only certain kinds of published parts of the winter (Baldwin and Kendeigh data and omit others, but to do this uni- 1938, King 1972). In contrast, Wood Pigeons formly is often difficult. Explicit details (Columba palumbus) in Scandinavia weigh should be given if weights and other measure- less in winter (Ljunggren 1968). Individual ments are taken from different published ducks near the northern limits of their winter sources ( Blake 1956). range decrease in weight through the winter Adequate samples of weights are unavail- while using fat reserves accumulated in fall able for many common species. For example, (Ryan 1972). Limited evidence suggests that I know of no published mean weights for in uniform tropical conditions resident species series of males and females for wild or do not vary seasonally in weight (Ward captive adult Ostriches (Strut&o camelus), 1969)) although such fluctuations do occur which are of special interest as the heaviest in tropical areas with dry seasons (McNeil living birds. During the past 40 years weigh- 1971). At least some species of birds taken ing has become common in banding and from the field and kept under constant collecting, and thousands of weights remain laboratory conditions continue to exhibit unpublished and dispersed in the files of seasonal fluctuations in weight for a year or banders and on specimen labels. Regrettably, longer, indicating the presence of endogenous most museum specimens collected before 1940 circannual rhythms that influence weight even lack data on weights, but collections at the in the absence of immediate environmental Museum of Vertebrate Zoology, University of stimuli (King 1968, Gwinner 1977). Under California, Berkeley, and the Museum of field conditions the timing of the endogenous Zoology, University of Michigan, Ann Arbor, rhythms is entrained by photoperiods to the contain many North American specimens natural cycles. The neuroendocrinological with field weights. bases for long-term endogenous cycles in weight remain poorly understood, but for the VARIATION WITHIN SPECIES White-throated Sparrow (Zonotrichia albicollis) experiments indicate that changes in the Daily. The weight of many birds fluctuates timing of release of corticosterone and pro- during a day with daily increases of 5 to 10% lactin control seasonal variations in fat stores ( exceptionally 15% ) over minimal weight (Meier and Burns 1976). occurring in many small land birds of both In many species reproduction, including temperate and tropical regions (Baldwin and egg production, incubation, and parental care Kendeigh 1938, Snow and Snow 1963, Ward of young, makes major energy demands some- 1969, King 1972, Blem 1976). Weight is times resulting in loss of weight; Ricklefs usually greatest in late afternoon and least (1974) cited examples for grouse and finches. after a night of fasting. This daily cycle in For the female Snow Goose (Chen caerules- weight is due to variation in gut contents, tens ) , accumulation of nutrient reserves, fat deposits, size of various organs, glycogen reflected in body weight prior to breeding, is stores, and other factors (King 1972, Blem an important factor in determining clutch 1976). In winter many small birds must feed size and even survival of the bird through the daily to survive the following night (King breeding season (Ankney and MacInnes 1972, Blem 1976) though larger birds can 1978). Marked shifts in the weight of females live longer without food (Kendeigh 1945). are in some cases associated with the stage In summer at high latitudes in continuous of egg production (Calder and Rowe 1977). daylight, birds can feed at any time and In certain penguins, fat reserves increase BODY WEIGHTS OF BIRDS 195 before incubation, and weight then declines Age. In many species, immature birds re- as the fat is consumed. As would be expected, main lighter than adults after the end of birds that incubate continually for days or parental care. Mueller et al. (1976) sug- weeks show major decreases in weight as in gested that such lower weight and a lower Emperor Penguin ( Aptenodytes forsteri ), wing loading of immature Goshawks (AC- which loses up to 40% of body weight (Le cipiter gent&) may reduce energy expendi- Maho 1977). In contrast to such extremes ture and thus lessen the need for prey when are birds that carry only small reserves of fat foraging behavior has not yet matured. In during much of the breeding season such as contrast are species whose young outweigh passerines in deciduous forests of New adults for a brief time after fledging, e.g., Hampshire during years of relatively abun- some seabirds in which a high weight at dant insect food (Holmes 1976); in this case fledging may provide extra energy reserves it would be interesting to know the levels of to sustain the young while they learn how to fat reserves in summers when food is less forage (Lack 1968). readily available. Year-to-year variations. Birds often vary in Changes in weight during molt differ weight from year to year depending on cli- markedly among taxa. Species in which molt mate and food availability (Coach et al. interferes with feeding can lose considerable 1960, Redfield 1973, Decoux 1976). Such weight (e.g., penguins; Williams et al. variations have apparently not yet been re- 1977). The extreme contrast is provided by ported for small birds (less than 25 g) but species that become heavier during molt can be expected to occur. [e.g., Bullfinches (Pyrrhula pyrrhula) ; New- Sexual dimorphism. In most avian species ton 19661. males are larger (Amadon 1959) as indicated Migrants exhibit some of the greatest by linear measurements and frequently con- weight fluctuations. Although some begin firmed by weights. In many species the migrating with little or no extra fat reserves sexual differences are slight, however, and (Odum et al. 1961, D. W. Johnston 1966, females during egg formation often outweigh Berthold 1975)) long-distance migrants typi- the males (Amadon 1959). Females are con- cally accumulate large fat deposits just prior sistently heavier in tinamous, the parasitic to long flights over unfavorable habitats, Black-headed Duck (Heteronetta atricapillu), e.g., oceans or deserts for landbirds. In some some ratites, certain hawks and owls, button species at least, circannual rhythms strongly quail, a number of Charadriiformes, some influence the timing of weight increase for hummingbirds, and a few dicaeids (Amadon migration (Gwinner 1977). The extent of 1959, Weller 1967, Snyder and Wiley 1976). weight gain before migration appears to be The adaptive significance of sexual size related to the distance to be flown (Odum dimorphism doubtless varies among taxa and et al. 1961, Berthold 1975) and tends to be remains poorly understood and controversial greatest for those parts of the migration that with authors differing on the possible roles are fastest and most precise temporally. For of sexual differences in aggressiveness, long migratory flights by small birds, weight parental care, energetics, and foraging (Weller can increase from 50% to 100% above non- 1967, Selander 1972, Hespenheide 1973, migratory values. Although fat as a major Downhower 1976, Snyder and Wiley 1976, energy source accounts for most of the weight Amadon 1977). An analysis by R. F. changes during migration, weights of fat-free Johnston et al. (1972) revealed that sexual components also change (e.g., see Rogers and dimorphism in weight of House Sparrows Odum 1966, Fry et al. 1970, Berthold 1975). (Passer domesticus) involves not only sexual In addition, fat-free weights can differ be- selection but also sexual differences in re- tween spring and fall (King 1963). During sponse to selection by climatic variables as prolonged migratory flight over inhospitable indicated by a severe winter storm that environments, birds may become emaciated, favored males of larger size but females of sometimes weighing less than ordinary fat- intermediate size. free levels due to decrease in both fat and Geographic variation. Weights of a species other components (Rogers and Odum 1966, often vary geographically. The Canada Pennycuick 1975). Weight increases before Goose (Branta canadensis) is a well-known, migration are often proportionately greater dramatic example in which birds of the for birds flying into relatively severe climates, largest subspecies are, within a sex, two to e.g., in north temperate birds flying north in three times heavier than those of the smallest spring as opposed to south in fall (King subspecies (Palmer 1976), if indeed such ex- 1963, Berthold 1975). tremes do still belong to a single species. In 196 GEORGE A. CLARK,JR. another example, the Ipswich Sparrow be least in the center of the geographic range (Passer&us sandwichensis princeps) , which and to rise peripherally. He considered the breeds predominantly on Sable Island off region of lowest weight to be that of maximal Nova Scotia, averages slightly more than adaptation of a species and also that occupied 25.5 g yet interbreeds to a limited extent on the longest. Correspondingly, the higher the mainland with a Savannah Sparrow popu- peripheral weights indicated both lesser lation (P. s. sawanna) averaging less than adaptation and more recent occupation. I 26 g (Stobo and McLaren 1975). suggest that the species studied by Salt The intraspecific tendency for landbirds to (1963) be reexamined to look for adaptations weigh more in the cooler and drier parts of to local climates (cf. James 1970) which are their range (Rand 1961a, Tomlinson 1975), presumably more severe in peripheral areas termed Bergmanns’ Rule, has been studied and thus favor greater energy stores in those mainly with wing lengths (James 1970), but areas. In addition, independent evidence weights vary similarly in many cases (Rand should be sought for the historic directions 1961a). Indeed, longer wing lengths may in of range occupation. The migratory status of some cases be closely associated with greater most temperate and arctic species greatly weights for reasons of aerodynamic efficiency complicates the analysis of geographic vari- (Blem 1975). The trend to greater weight in ations in weight by requiring consideration cooler and drier climates occurs not only over of seasonal differences. latitude and longitude but also with altitude Johnston and Selander (see R. F. Johnston (Moreau 1944, Nottebohm 1975, Koster 1976). 1972) found that largely nonmigratory popu- The adaptive significance of geographic lations of House Sparrows in North America gradients in weight has been and continues and Europe generally follow Bergmanns’ to be highly controversial. Although larger Rule except in far northern North America, birds have relatively less surface area and where winter day length may limit feeding hence relative advantages in heat retention, time and hence body weight (Johnston 1972). this feature alone does not account for larger The geographic size variation in North body sizes in cooler climates (McNab 1971, American populations arose within a century Calder 1974). One apparent major advantage after the species was introduced from of larger size in cooler climates is a lessened Europe. Johnston and Selander attributed likelihood of starving to death in severe this variation in part to regional genetic dif- weather due to greater efficiency in use of ferences produced by natural selection, but stored energy reserves (Calder 1974, Ketter- obtaining direct evidence for a genetic basis son and Nolan 1976). Furthermore, larger for the phenotypic variation has been difficult individuals may carry proportionately greater (Johnston 1975). In contrast, Koster (1976) fat reserves (Blem 1973) and possibly derive interpreted altitudinal weight differences of benefits of added insulation from their large apparently recent origin in South America fat stores (Blem 1974). By contrast, in hot Smooth-billed Anis (Crotophaga ani) and climates the relatively greater surface area of Tropical Kingbirds (Tyrannus melancholicus) small birds should be advantageous in as probably not inherited. Laboratory ex- facilitating cooling (James 1970). However, periments on captive nidifugous birds from McNab (1971) has emphasized geographic different geographic areas reared under variations in food size and competitors as various climatic conditions might provide determinants of latitudinal gradients in additional evidence on possible genetic bases weights. Although he mentioned also a for geographic variation in weights. For ex- tendency for insular populations to be larger ample, Bobwhites ( CoZinus virginianus) tend than mainland representatives of a species, to be heavier in more northern localities there are many contrary cases (Grant 1968), (Ripley 1960)) and the effect of genotype as and the determinants of body weight in in- opposed to climate on weight might be tested sular populations are not well understood. by rearing northern birds under southern Numerous exceptions to Bergmanns’ Rule conditions and vice versa. warrant special attention (Rand 1961a, Niles 1973). In parts of the western continental EVOLUTION OF TAXONOMIC U.S., mountainous topography favors great DIFFERENCES IN WEIGHTS variation in climate over relatively short distances. Not surprisingly, many species Independent gains and decreases of weight there do not follow Bergmanns’ Rule (Rand have occurred repeatedly during evolution as 1961a, Salt 1963). For 53 such species Salt shown by marked weight differences between (1963) found that breeding weights tend to species within and among many families and BODY WEIGHTS OF BIRDS 197 orders (Clark 1973). Among species with Rahn et al. (1975) calculated from egg similar body shapes the relatively smaller volumes that the largest of the fossil elephant- surface area of larger birds reduces buoyancy birds ( Aepyornithidae) might have weighed for flight (Storer 1955). Accordingly, soaring 1000 kg, a value twice that estimated by and gliding species tend to have large surface Amadon (1947) on the basis of body lengths. areas for flight relative to their weights However, there is no clear evidence as to (Hartman 1961). Among diving birds, which estimate is more accurate, and weight greater density (weight/volume) can counter estimates for fossils that are unlike modern buoyant tendencies and thus reduce the genera are generally difficult to test. Factors energy cost in diving (Storer 1960, Simpson limiting maximal size for both flying and 1976:45). For example, the Green-winged flightless birds have not yet been critically Teal (Anas crecca carolinensis), a dabbling analyzed. Biotic environmental factors in duck, and the Bufflehead (Bucephala al- evolution have presumably generally re- beola), a diver, have similar body lengths, but strained weights below the maxima that the male Bufflehead regularly outweighs the might be attainable if only physical factors male teal by 1.2 times or more (data from were limiting. Palmer 1976). Ideally volumetric data should be used in such comparisons, but they are USES OF WEIGHTS unavailable. Reduced buoyancy facilitates diving but hinders flight; the least buoyant Standards for body size. A standard for body birds are flightless divers such as penguins size is frequently useful in comparing either ( Simpson 1976). individuals or species, and numerous refer- Biotic factors including size of food and ences discuss this subject for birds (Amadon its distribution greatly influence the evolution 1943, Calder 1974). Body size has usually of taxonomic differences in weight. Larger been measured with weights or linear dimen- species have advantages over smaller ones in sions, either of which can be useful depending usually eating not only larger food items but on the circumstances. also a wider range of sizes of food (Wilson Weight summarizes the total biomass of an 1975). Although within a species social individual and is probably the most con- dominance is often not directly associated with venient standard for energetic comparisons. weight ( Swingland 1975)) heavier species Furthermore, in comparing properties of usually dominate lighter ones (Morse 1974) distantly related taxa, e.g., woodpeckers and and thus are likely to win in direct competi- nuthatches, weight may be a better standard tion for food or space. Smaller species have of body size than any linear measurement. advantages in being able to use food items, Weights are handicapped, however, because nest sites, and perches too small for heavy of variation within individuals and within birds, and small birds can also use denser species. For determining the larger of two vegetation for foraging and protection. Dif- populations with very simiIar mean weights, ferences in weight among closely related, it is sometimes more practical to use numerous syntopic species help to reduce the likeli- linear measurements (e.g., of long bones) hood of interspecific competition (Hespen- instead of weights. heide 1973). If density is uniform, weight is proportional The lightest of birds are certain humming- to volume which in turn is proportiona to birds, a few of which weigh only about 2 g the cube of a linear dimension. Hence, for (Hartman 1961). Lasiewski ( 1963) reported comparing linear dimensions the cube root that the Cuban Bee Hummingbird (Calypte of weight can be an advantageous standard in helenae) weighs as little as 1.7 g, perhaps providing a clearer indication of proportions the smallest of all birds. Both miniaturization and in reducing variation in weights to a and energetics appear to limit minimal level more like that of linear measurements weights for birds (Kendeigh 1972, Greenewalt ( Amadon 1943). 1975). The heaviest of living flying birds When weights are unavailable or inade- reach 12 kg and include Mute Swans (Cygnus quate, linear measures such as wing length olor), condors ( VuZtur) ) and bustards must represent body size. Although wing ( Ardeotis), although the Pleistocene fossil length often correlates with weight within a vulture Teratornis merriami and the Miocene species (Rand 1961a, b; but see Owen 1962)) seabird Osteodontornis were larger. The exceptions are frequent. For example, Grant largest extant flightless birds are Ostriches, (1965) found wing length to be a poor index adult males of which often exceed 100 kg of body weight in intraspecific comparisons and sometimes more than 140 kg in captivity. between birds of the Tres Marias Islands and 198 GEORGE A. CLARK, JR. mainland Mexico. Linear measures along the and corvids ( Corvidae), but I know of no vertebral column have often been used to case in which weights were explicitly used represent body size. However, these measure- as a taxonomic character among the higher ments can also mislead due to differences in categories. Similar adult weights of different column length relative to weight, as in the species might conceivably be a shared, de- two closely related species of murres (U&z; rived character indicating evolutionary af- Spring 1971). In other cases, addition of finities, but weights themselves are simple measurements of numerous bones has yielded characters and readily subject to convergence. a so-called skeletal sum, or multiplication of Assessing physiological condition. Weight three skeletal measurements has formed an changes often reflect critical events, as in sick artificial “cubic” measurement (see Riiger individuals undergoing marked declines. 1972 for references). Such computed indices Weights may indicate levels of metabolic should be compared with actual weights, or reserves of breeding individuals (Korschgen their cube roots, to be confident that the 1977). Calder and Rowe ( 1977)) for example, indices do indeed represent overall size found indications that changes in weight of (Riiger 1972). Where many linear measure- a female Brown Kiwi (Apteryx uustrulis) ments are obtainable, as on skeletons, were closely associated with stages of egg principal components analysis yields an ab- production. stract index of size and hence weight, though Weights have also been used to calculate also influenced by shape (R. F. Johnston potential flight ranges of certain migrant 1972, Niles 1973). species in which wing length correlates A major analytic method both within and strongly with fat-free body weight. Measure- among species is the allometric description of ments of wing length and total body weight aspects of structure, physiology, and behavior then enable estimation of fat reserves and with body weight as the standard for com- hence of potential flight range (Odum et al. parison (Calder 1974). Examples of features 1961, McNeil and Cadieux 1972). However, thus described include basal metabolism, wing lengths and fat-free weights are poorly dimensions related to flight, respiration, correlated in other species so that the method circulation, and temperature (Calder 1974, is not always applicable (Moreau and Dolf Greenewalt 1975). Ecological properties such 1970, Berthold 1975). as home range size (Calder 1974) and be- Community analysis. Weights have been havioral features such as characteristics of used in analyses of the factors that influence vocalizations (Bergmann 1976) can also be differences in species diversity between com- stated allometrically, although the scatter munities (e.g., Karr 1968, 1971, 1976, Pearson sometimes exceeds that for physiological 1975, Faaborg 1977). Weights and census properties ( Calder 1974). Allometric equa- data have often been combined to calculate tions are basically descriptive but within the total weight (biomass) of a particular empirical limits may predict properties of species or group of species in an area. For species not studied directly. However, caution example, Willson (1974) found that total is advisable in extrapolating beyond empirical biomass of birds in Illinois grassland, shrub, limits or in assuming causation on the basis and forest communities was not correlated of correlation. For example, both feather with productivity of the vegetation or of the number and egg weight can be significantly invertebrates in those communities. In an- correlated with body weight and with each other case, Salt (1957) assessed the relative other, but this does not indicate that egg efficiency of temperate zone communities weight determines feather number or vice on the basis of their proportion of large birds. versa. As larger birds have a greater efficiency per Systematics. Differences in weights can gram (Calder 1974), a given amount of food sometimes serve along with other features to can sustain a larger biomass of heavier birds separate taxa (Amadon 1943, Moreau 1944). than of lighter ones. In late successional For example, Ripley (1960) used weights in stages of Wyoming coniferous forests, Salt distinguishing subspecies of the Bobwhite. found relatively more large birds and hence Fisher (1952) presented data showing that by his criterion a greater efficiency for the Antarctic Fulmars (Fulmarus ghzciaboides) avifauna as a whole compared with earlier on the average outweigh Northern Fulmars successional stages. Moreover, he suggested ( F. gZaciaZis gZaciaZis), although this differ- that birds might regularly serve as indices of ence has apparently not been used in their metabolism and efficiency for entire biotic systematics. Many higher categories are also communities, a possibility that merits further separable by weights, e.g., titmice (Paridae) study. BODY WEIGHTS OF BIRDS 199

Many ornithologists have used body weights from the literature. Possible effects of handling to estimate energy consumption by avian live birds and of postmortem changes are communities over periods of time. The cal- briefly considered. Weight variation within culations require census data on number of species is discussed in relation to time of day, individuals per species, their body weights, season, migration, year, age, sex, geography, allometric equations relating weight to basal and other factors. Evolutionary specializations metabolism, and estimates of other energy include increased buoyancy in gliding and costs to assesstotal energy requirements (see, soaring species and reduced buoyancy in for example, Wiens and Innis 1974, Wiens divers. Rody weight is closely related evolu- and Scott 1975, Holmes and Sturges 1975). tionarily to the foods consumed and to the Although several assumptions must be made, structure of habitats. Weights are useful as the results lead to predictions that are standards for body size, in systematics, for potentially independently verifiable, e.g., assessing the physiological condition of birds, through study of the feeding rates of in- and in ecological community analysis. dividual birds. ACKNOWLEDGMENTS SOME TOPICS FOR FUTURE STUDIES This review was initially suggested by P. R. Stetten- My review of this subject disclosed many heim, who continued to provide valuable comments unsolved problems, several of which have throughout its preparation. D. Amadon, C. R. Blem, M. H. Clench, F. C. James, D. W. Johnston, J. R. already been mentioned. Weights have been Karr, L. F. Kiff, D. M. Niles, and R. L. Zusi gave most extensively reported for European and valuable aid in writing the manuscript. G. E. Watson North American birds and additional data generously made available the facilities of the Na- are especially needed for other avifaunas. tional Museum of Natural History, Washington, D.C. Many other individuals, too numerous to list here, For all regions, knowledge of geographic assisted by providing literature citations, reprints, and variation in weights is deficient due to lack informative discussion. of data, particularly for breeding and wintering populations. Relatively extensive data are LITERATURE CITED available for a few species, such as the House A~IADON, D. 1943. Bird weights as an aid in tax- Sparrow, but even for these species large onomy. Wilson Bull. 55: 164-177. populations remain reIativeIy unstudied, e.g., AhlADOx, D.‘ 1947. An estimated weight of the the House Sparow populations of the southern largest known bird. Condor 49: 159-164. hemisphere. Amadon (1943) provided the AX~ADON, D. 1959. The significance of sexual dif- most recent general discussion for birds on ferences in size among birds. Proc. Am. Philos. Sot. 103:531-536. the relative variability of weights both within AMADON, D. 1977. Further comments on sexual and among species, and the subsequently s6i;; dimorphism in birds. Wilson Bull. 89:619- published data, widely scattered through the literature, have not been comprehensively ANKNEY, C. D., ANU C. D. MACINNES. 1978. Nu- trient reserves and reproductive performance of analyzed. female Lesser Snow Geese. Auk 95:459-471. Much research is needed on the deter- BALDWIN, S. P., AND S. C. KEN~EIGH. 1938. Varia- minants of weight of different species in tions in the weight of birds. Auk 55:416-467. relation to their food and habitat require- BEHGER, E. J., JR. 1968. Accuracy of Pesola spring ments. Rensch (1960) reviewed several scales and Harvard trip balances. EBBA News 31: 107-108. papers reporting better learning abilities for BERGMANN, H.-H. 1976. Konstitutionsbedingte birds from heavier populations or species (see Merkmale in Geslngen und Rufen europ%scher also Stichmann 1962); such a tendency if Grasmiicken (Gattung Sylvia). Z. Tierpsychol. widespread is of general interest in the evo- 42:315329. lution of body weights. The buoyancy dif- BERTHOLD, P. 1975. Migration: control and metabolic physiology, p. 77-128. In D. S. Farner, ferences among diving birds have not been J. R. King, and K. C. Parkes reds.], Avian biol- extensively studied. Weights should be in- ogy. Vol. 5. Academic Press, New York. vestigated as indicators of nutrient reserves BLAKE, C. H. 1956. Weight changes in birds. Bird- and of energy requirements for individuals Banding 27:16-22. and populations. Moreover, weights should BLEM, C. R. 1973. Geographic variation in the bio- continue to be of major importance in studies energetics of the House Sparrow. Omithol. Monogr. 14:96-i-121. of community organization. BLEM, C. R. 1974. Geographic variation of thermal conductance in the House Sparrow Passer do- SUMMARY mesticus. Comp. Biochem. Physiol. 47A: 101-108. BLEM, C. R. 1975. Geographic variation in wing- This survey covers procedures and problems loading of the House Sparrow. Wilson Bull. 87: in obtaining body weights in the field and 543-549. 200 GEORGE A. CLARK, JR.

BLEM, C. R. 1976. Patterns of lipid storage and birds and its relationship to climate. Ecology 51: utilization in birds. Am. Zool. 16:671-684. 365390. BUB, H. 1967. Vogelfang und Vogelberingung. Teil JOHNSTON, D. W. 1966. A review of the vernal fat 1. Ziemsen, Wittenberg Lutherstadt. deposition picture in overland migrant birds. CALDEH, W. A., III. 1974. Consequences of body Bird-Banding 37: 172-183. size for avian energetics, p. 86-144. In R. A. JOHNSTON, R. F. 1972. Ecological differentiation in Paynter, Jr. [ed.], Avian energetics. Publ. Nuttall North American birds, p. 101-126. In R. T. Allen Ornithol. Club No. 15. and F. C. James reds.], A symposium on ecosys- CALIIEH, W. A., III, AND B. ROWE. 1977. Body tematics. Univ. Arkansas Mus. Occas. Pap. No. 4. mass changes and energetics of the Kiwis’ egg JOHNSTON, R. F. 1975. Studies in phenetic and ge- cycle. Notornis 24: 129-135. netic covariation, p. 333-353. In G. Estabrook CLARK, G. A., JR. 1973. Convergence and parallel- led.], Proceedings of the 8th Int. Conf. of Nu- ism in the evolution of birds. Biologist 55:112- merical Taxonomy. Freeman, San Francisco. 118. JOHNSTON, R. F., D. M. NILES, AND S. A. ROHWF,H. CLENCH, M. H., AND R. C. LEBEHMAN. 1978. 1972. Hermon Bumpus and natural selection in Weights of 151 species of Pennsylvania birds the House Sparrow Passer domesticus. Evolution analyzed by month, age, and sex. Bull. Carnegie 26:20-31. Mus. Nat. Hist. 5. KAHH, J. R. 1968. Habitat and avian diversity on COOCH. F. G.. G. M. STIHHETT. AND G. F. BOYEH. strip-mined land in east-central Illinois. Condor 1960. Aitumn weights of ’ Blue Geese (Chen 70:348-357. caerulescens j. Auk 77:460465. KARH, J. R. 1971. Structure of avian communities DECOUX, J. P. ’ 1976. Regime, comportement ali- in selected Panama and Illinois habitats. Ecol. mentaire et regulation ecologique du metabolisme Monogr. 41:207-233. chez Colius stiiatus. Terre et Vie 30:395-420. KAHH, J. R. 1976. Seasonality, resource availability, DOWNHO~EH. 1. F. 1976. Darwins’ Finches and and community diversity in tropical bird com- I I the evolution of sexual dimorphism in body size. munities. Am. Nat. 110:973-994. Nature 263:558-563. KENDEIGH, S. C. 1945. Resistance to hunger in ELLIS. D.. AND T. VARNEY. 1974. Usinrr telemetrv birds. I. Wildl. Manage. 9:217-226. th stidy the”Golden Eagle. Int. Foundation Tel;- KENDEIGH, s. C. 1972. Energy control of size limits metering J. 1:1418. in birds. Am. Nat. 106:79-88. FAABOHG, J. 1977. Metabolic rates, resources, and KETTERSON, E. D., AND V. NOLAN, JR. 1976. Geo- the occurrence of nonpasserines in terrestrial graphic variation and its climatic correlates in avian communities. Am. Nat. 111:903-916. the sex ratio of eastern-wintering Dark-eyed FISHER, H. I. 1955. Avian anatomy, 1925-1950, Juncos (Junco hyemalis hyemalis). Ecology 57: and some suggested problems, p. 57-104. In 679-693. A. Wolfson [ed.], Recent studies in avian biol- KING, J. R. 1963. Autumnal migratory-fat deposi- ogy. Univ. of Illinois Press, Urbana. tidn in the White-crowned Sp&row. Proc. XIII FISHER. 1. 1952. The fulmar. Collins. London. Int. Ornithol. Congr. ( 1962) :940-949. FRY, 6.” H., 1. S. ASH, AND I. J. F&RGUSON-LEES. KING, J. R. 1968. C$cles of fai deposition and molt 1970.’ ~Spring weights of some Palaearctic mi- in White-crowned Sparrows in constant environ- grants at Lake Chad. Ibis 112:58-82. mental conditions. Comp. Biochem. Physiol. 24: GILE~, R. H., JR. 1963. Instrumentation in wildlife 827-837. investigations, p. 1-21. In H. S. Mosby led.], KING, J. R. 1972. Adaptive periodic fat storage by Wildlife investigational techniques. Second ed. birds. Proc. XV Int. Ornithol. Congr. (1970): Edwards, Ann Arbor, Michigan. 200-217. GRANT, P. R. 1965. A systematic study of the ter- KONTOGIANNIS, J. E. 1967. Day and night changes restrial birds of the Tres Marias Islands, Mexico. in body weight of the White-throated Sparrow, Postilla 90: l-106. Zonotrichia albicollis. Auk 84:390-395. GRANT, P. R. 1968. Bill size, body size, and the KOHSCHGEN, C. E. 1977. Breeding stress of female ecological adaptations of bird species to com- eiders in Maine. J. Wildl. Manage. 41:360-373. petitive situations on islands. Syst. Zool. 17:319- K~~STER, F. 1976. iiber die HGhenanpassung von 333. Crotophaga ani und Tyrannus mel&holi&s in GHEENEWALT, C. H. 1975. The flight of birds. den Anden Kolumbiens. T. Ornithol. 117:75-99. Trans. Am. Philos. Sot. N. S. 65( 4) : l-67. LACK, D. 1968. Ecological idaptations for breeding GWINNER, E. 1977. Circannual rhythms in bird in birds. Methuen, London. migration. Annu. Rev. Ecol. Syst. 8:381405. LASIEWSKI, R. C. 1963. The energetic cost of small HAHTMAN, F. 1961. Locomotor mechanisms of size in hummingbirds. Proc. %I11 Int. Omithol. birds. Smithson. Misc. Collect. 143:1-91. Coner. ( 1962 1: 1095-1103. HESPENHEIDE, H. A. 1973. Ecological inferences LE:BERM~N, k. C.: AND M. A. STERN. 1977. Han- from morphological data. Annu. Rev. Ecol. Syst. dling-induced shock in migrant songbirds. North 4:213-229. Am. Bird-bander 2:5054. HOLMES, R. T. 1976. Body composition, lipid re- LE MAIIO, Y. 1977. The Emperor Penguin: a strat- serves and caloric densities of summer birds in egy to live and breed in the cold. Am. Sci. 65: a northern deciduous forest. Am. Midl. Nat. 96: 680-693. 281-290. LJUNGG~N, L. 1968. Seasonal studies of Wood HOLMES, R. T., ANI) F. W. STURGES. 1975. Bird Pigeon populations. Viltrevy 5:435-504. community dynamics and energetics in a north- MCNAB, B. K. 1971. On the ecological significance ern hardwoods ecosystem. J. Anim. Ecol. 44: of Bergmanns’ Rule. Ecology 52:845-854. 175-200. MCNEIL, R. 1971. Lean-season fat in a South IRVING, L. 1960. Birds of Anaktuvuk Pass, Kobuk, American population of Black-necked Stilts. Con- and Old Crow. U.S. Natl. Mus. Bull. 217. dor 73 :472-475. JAMES, F. C. 1970. Geographic size variation in McNEn., R., AND F. CADIEUX. 1972. Numerical BODY WEIGHTS OF BIRDS 201

formulae to estimate flight range of some North RIPLEY, T. H. 1960. Weights of Massachusetts American shorebirds from fresh weight and wing quail and comparisons with other geographic length. Bird-Banding 42: 107-113. samples for taxonomic significance. Auk 77:445- MEIER. A. H.. AND 1. T. BURNS. 1976. Circadian 447. hormone rhythms in lipid regulation. Am. Zoo]. ROGERS, D. T., JR., AND E. P. ODUM. 1966. A study 16: 649-659. of autumnal postmigrant weights and vernal fat- MOORE, N. C. 1953. A balance for weighing tits tening of North American migrants in the tropics. without capture. Br. Birds 46: 103-105. Wilson Bull. 78:415-433. MOREAU, R. E. 1944. Some weights of African and R&ER, A. 1972. Funktionell-anatomische Unter- of wintering Palearctic birds. Ibis 86:16-30. suchungen an Spechten. Z. wiss. Zoo]. 184:63- MOREAU, R. E., AND R. M. DOLF. 1970. Fat, wa- 163. ter, weights and wing-lengths of autumn migrants RYAN, R. A. 1972. Body weight and weight changes in transit on the northwest coast of Egypt. Ibis of wintering diving ducks. J. Wild]. hlanage. 36: 112:209-228. 759-765. MORSE, D. H. 1974. Niche breadth as a function SALT, G. W. 1957. An analysis of avifaunas in the of social dominance. Am. Nat. 108:818-830. Teton Mountains and Jackson Hole, Wyoming. MUELLER, H. C., AND D. D. BERGER. 1966. Analy- Condor 59:373-393. ses of weight and fat variations in transient SALT, G. W. 1963. Avian body weight, adaptation, Swainsons’ Thrushes. Bird-Banding 37:83-112. and evolution in western North America. Proc. MUELLER, H. C.. 13. D. BERGER. AND G. ALLEZ. XIII Int. Ornithol. Coner. ( 1962) :905-917. 1976: Age and sex variation in the size of Gos- SELANDER, R. K. 1972. Sexual selection and di- hawks. Bird-Banding 47:310-318. morphism in birds, p. 180-230. In B. Campbell NEWTON, I. 1966. The moult of the Bullfinch led.], Sexual dimorphism and the descent of man. Purrhula nurrhula. Ibis 108:41-67. Aldine, Chicago. NICE, -M. M. ’ -1938. The biological significance of SINIPSON, G. G. 1976. Penguins. Past and present, bird weights. Bird-Banding 9: l-11. here and there. Yale Univ. Press, New Haven. NILES, D. M. 1973. Adaptive variation in body size Ssow, D. W., AND B. K. SNOW. 1963. Weights and and skeletal proportions of Horned Larks of the wing-lengths of some Trinidad birds. Zoologica southwestern United States. Evolution 27:405- 48: 1-12. 426. SNYDER, N. F. R., AND J. W. WILEY. 1976. Sexual NOTTEBOHM, F. 1975. Continental patterns of song size dimorphism in hawks and owls of North variability in Zonotrichia capensis: some possible America. Ornithol. Monogr. 20. ecological correlates. Am. Nat. 109:605-624. SPRING, L. 1971. A comparison of functional and ODUM, E. P., C. E. CONNELL, AND H. L. STODDARD. morphological adaptations in the Common Murre 1961. Flight energy and estimated flight ranges (Uris aalge) and Thick-billed Murre (Uris of some migratory birds. Auk 78:515-527. lomvia). Condor 73: l-27. OWEN. D. F. 1962. Wing length. bodv weight. and STICHMANN, W. 1962. Transpositionsversuche mit geography. Wilson Buli 743185. ’ - ’ Haushuhnrassen stark verschiedener Korpergrosse. PALMER, R. S. IED.] 1976. Handbook of North Z. Tierpsychol. 19:290-320. American birds. Vols. 2 and 3. Yale Univ. Press, STOBO, W. T., AND I. A. MCLAREN. 1975. The Ips- New Haven. with Sparrow. Nova Scotian Institute of Science, PEARSON, D. L. 1975. The relation of foliage com- Halifax. plexity to ecological diversity of three Amazonian STORER, R. W. 1955. Weight, wing area, and skel- bird communities. Condor 77:453-466. etal proportions in three accipiters. Proc. XI Int. PENNYCUICK, C. J. 1975. Mechanics of flight, p. l- Ornithol. Congr. ( 1954) :287-290. 75. In D. S. Farner, J. R. King, and K. C. Parkes STORER, R. W. 1960. Evolution in the diving birds. [eds.], Avian biology. Vol. 5. Academic Press, Proc. XII Int. Ornithol. Congr. (1958) 3694-707. New York. SWINGLAND, I. R. 1975. The influence of weather PETTINGILL, 0. S., JR. 1970. Ornithology in lab- and individual interactions on the food intake of oratory and field. Fourth ed. Burgess, Minne- captive Rooks (Corvus frugilegus). Physiol. apolis, Minn. Zoo]. 48:295-302. RAHN, H., C. V. PAGANELLI, AND A. AR. 1975. Re- THOMSON, A. L. ]ED.] 1964. A new dictionary of lation of avian egg weight to body weight. Auk birds. McGraw-Hill, New York. 92:750-765. TOMLI?~TSON,R. E. 1975. Weights and wing lengths RAND, A. L. 1961a. Some size gradients in North of wild Sonoran Masked Bobwhites during fall American birds. Wilson Bull. 73:46-56. and winter. Wilson Bull. 87:180-186. RAND, A. L. 1961b. Wing length as an indicator VON BR~CKEL, K. 1973. Vergleichende Messungen of weight: a contribution. Bird-Banding 32:71- an lebenden und frischtoten Gartengrasmiicken 79. (Sylvia borin). J. Ornithol. 114: 114-122. RAPPOLE, J. H., AND D. W. WARNER. 1976. Rela- WARD, P. 1969. Seasonal and diurnal changes in tionships between behavior, physiology and the fat content of an equatorial bird. Physiol. weather in avian transients at a migration stop- Zoo]. 42 : 85-89. over site. Oecologica 26: 193-212. WELLER, M. W. 1967. Notes on plumages and REDFIELD, J. A. 1973. Variations in weight of Blue weights of the Black-headed Duck, Heteronetta Grouse (Dendragapus obscures). Condor 75: atricapiZZu. Condor 69: 133-145. 312321. WIENS, J. A., AND G. S. INNIS. 1974. Estimation RENSCH, B. 1960. Evolution above the species level. of energy flow in bird communities: a population Columbia Univ. Press, New York. bioenergetics model. Ecology 55: 730-746. RICKLEFS, R. E. 1974. Energetics of reproduction WIENS, J. A., AND J. M. SCOTT. 1975. Model esti- in birds, p. 152-292. In R. A. Paynter, Jr. led.], mation of energy flow in Oregon coastal seabird Avian energetics. Pub]. Nuttall Ornithol. Club populations. Condor 77:439-452. No. 15. WILLIAMS, A. J., W. R. SIEGFRIED, A. E. BURGER, 202 GEORGE A. CLARK, JR.

AND A. BERRUTI. 1977. Body composition and more extensive bibliography and supplements that energy metabolism of molting eudyptid penguins. have been filed in the Josselyn Van Tyne Memorial Camp. Biochem. Physiol. 56A:27-30. Library, Museum of Zoology, University of Michigan, WILLSON, M. F. 1974. Avian community organiza- Ann Arbor, and the library of the Division of Birds, tion and habitat structure. Ecology 55:1017- National Museum of Natural History, Washington, 1029. D.C. WILSON, D. S. 1975. The adequacy of body size as a niche difference. Am. Nat. 109:769-784. Biological Sciences Group, University of Connecticut, Storm, Connecticut 06268. Accepted for publication Hundreds of additional references are included in a 11 September 1978.’

Condor, 81:202 0 The Cooper Ornithological Society 1979

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