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We examined winter distribution and fidelity to wintering areas for the American Woodcock (Scolopax minor), which exhibits reversed, sexual size dimorphism. Bandrecovery data revealed no difference in winter distributions of different age/sex classes for woodcock from the same breeding ares. Similarly, band recoveries from woodcock banded on wintering grounds revealed no difference in fidelity to wintering sites. Males may winter north of a latitude that is optimal for survival based on physiological considerations, but they gain a reproductive advantage if they are among the first to arrive on the breeding grounds. This may explain our results, which indicate males and females have similar distribution patterns during winter. Received 5 December 1989, accepted 12 May 1990. MANY migratory bird species exhibit sexand age-specific differences in where they winter (see reviews in Ketterson and Nolan 1976, 1983; Nichols and Haramis 1980; Myers 1981). Three hypotheses have been invoked to explain differences. One concerns physiological differences associated with body size, another considers behavioral dominance of age/sex classes, and a third concerns differences in time of arrival on breeding grounds (see Hypotheses and Predictions). Unfortunately, most previous investigations of differential distribution patterns on the wintering grounds have been conducted on species for which the observed distributional differences are consistent with predictions of two or all three of these hypotheses. We investigated winter distribution patterns of American Woodcock (Scolopax minor). They are an appropriate choice for two reasons. First, the hypothesis of behavioral dominance among age/sex classes can likely be rejected a priori for this species, while the two remaining hypotheses yield opposite predictions (see Hypotheses and Predictions). Second, band-recovery data are available. Band-recovery data permit unambiguous inferences about distribution patterns during winter of birds from specific 2 Present address: U.S. Fish and Wildlife Service, Iroquois National Wildlife Refuge, Box 517, Alabama, New York 14003 USA. breeding areas (Nichols and Haramis 1980, Nichols et al. 1983, Perdeck and Clason 1983, Nichols and Hines 1987, Diefenbach et al. 1988a, b). Most studies of winter distribution patterns use samples (e.g. museum specimens) of birds obtained at specific wintering locations without prior knowledge of their origin on the breeding grounds. The geographic variation in age or sex ratios of such samples is ambiguous. Previous investigators have inferred that such variation reflected variation in wintering-ground destination among birds from the same breeding areas. An alternative explanation is that geographic variation in age or sex ratios exists on the breeding grounds and that birds from the same breeding areas migrate together to the same wintering areas (see Nichols and Hines 1987: 35). In this instance, age or sex ratios on the wintering grounds simply reflect ratios on breeding grounds, and proposed explanations of different migration patterns may be unnecessary. In addition to examining winter distribution of the different age/sex classes of American Woodcock, we tested hypotheses about ageand sex-specific variation in fidelity to wintering areas. To date, such questions about fidelity to wintering grounds have been restricted primarily to waterfowl (Nichols et al. 1983, Nichols and Hines 1987, Diefenbach et al. 1988a, b). Our objectives were to test two null hypotheses. First, male and female woodcock from the 745 The Auk 107: 745-749. October 1990 This content downloaded from 157.55.39.220 on Fri, 02 Sep 2016 05:26:05 UTC All use subject to http://about.jstor.org/terms 746 DIEFENBACH ET AL. [Auk, Vol. 107 same breeding areas have the same pattern of distribution in winter. Second, male and female woodcock have similar degrees of fidelity to specific wintering areas. Both of these hypotheses were tested for young, adult, and both ageclasses combined.

The American Woodcock (Scolopax minor) is one of the earliest ground-nesting birds in the northeastern United States. In Maine, nesting begins in early April when temperatures can drop below freezing and significant snowfall can accumulate. Nests are usually in open woods, where eggs are laid on the ground in a shallow depression (Pettingill 1936, Mendall and Aldous 1943, Sheldon 1967). Peak hatching occurs in early May (Dwyer et al. 1982), when temperatures are cool and precipitation is common. Woodcock chicks are dependent on the female for most of their food for at least seven days after hatching (Gregg 1984). During cool, wet weather, chicks require constant brooding by females; prolonged periods of inclement weather may lead to substantial mortality of chicks (Dwyer et al. 1988). This reproductive strategy led Pettingill (1936), Mendall and Aldous (1943), and Sheldon (1967) to speculate that renesting by American Woodcock is common, although they could not document this behavior. Renesting would seem necessary to maintain adequate recruitment because American Woodcock clutches are small (3-4 eggs), nest success is 50-67% (Mendall and Aldous 1943, Gregg 1984), and chick survival is 59% (Dwyer et al. 1988). Renesting after loss of a clutch has been documented for other shorebirds, including the Eurasian Woodcock (Scolopax rusticola; Hirons and Owen 1982), plovers (Charadrius spp.; Warriner et al. 1986), Spotted Sandpipers (Actitis macularia; Lank et al. 1985, Oring and Lank 1986), Killdeer (Charadrius vociferus; Brunton 1988), and Rednecked Phalaropes (Phalaropus lobatus; Reynolds 1987). Some shorebird species are polyandrous (Schamel and Tracy 1977, Lank et al. 1985, Oring 1985, Reynolds 1987), and a few species are double-brooded (Brunton 1988). Only circumstantial evidence of late-nesting birds (Ammann 1967, Parris 1983) and prolonged brood seasons (Rabe 1979) suggest that woodcocks will renest. We present the first definitive records of renesting by American Woodcocks during a single nesting season. We conducted this study on the 6,850-ha Baring unit of Moosehorn National Wildlife Refuge (NWR) near Calais, Maine, on the New Brunswick border. Dwyer et al. (1988) described the study area in detail. Female woodcocks were captured in mist nets on courting areas. Females on nests and those with broods were located by a pointing dog and captured with hand nets (Ammann 1977). All nesting females and females with broods '5 days old were radio-marked. Females were aged by wing-plumage characteristics (Martin 1964) and classified as 1 year old (SY) or -2 years old (ASY). We weighed each bird at the time of capture and attached a 3.5-4 g transmitter to its back by livestock-tag cement and a single-loop wire harness (Derleth 1986). We located birds daily from vehicles or on foot with portable receivers and handheld antennas. Lost birds were located from light, fixed-wing aircraft with antennas attached to the struts (Gilmer et al. 1981). We flew transects 3.2 km apart across the study area and ? 16 km beyond its borders. Transmitter signals were detectable ?0.8 km from the ground and 20 days of age. Her reproductive tract contained

Live-trapped, adult American Woodcock (Scolopax minor) were tested in a series of laboratory experiments designed to evaluate the role of soil as a proximal cue for selecting feeding sites and to investigate foraging strategies for capturing earthworms (Lumbricidae). Foraging trials were conducted in a circular arena and showed that color, which tends to be correlated with the soil types and moisture regimes preferred by earthworms, was an important proximal cue for selecting feeding sites. Woodcock captured earthworms most efficiently in areas of relatively high prey density, because they used a nonrandom search pattern following an initial capture.

MANY bird studies have shown individual differences in vocalizations within one species. For the most part such spectrographic studies deal with passerine songs, but some work with game birds has been done. Beightol and Samuel (1973) recently completed an analysis of American Woodcock (Philohela minor) vocalizations and showed that individual birds were readily identified by their voice prints. Williams (1971) also found individuality in calls of Bobwhite (Colinus virginianus). If identification of the drums of individual Ruffed Grouse (Bonasa umbellus) were possible then it could be used as a new "tool" for study of longevity and movements of this bird. The drum of the Ruffed Grouse is a nonvocal sound produced by rapid wing strokes (for an exact description of this display, see Hjorth 1970: 225-232). Aubin (1972) examined this nonvocal form of communication and concluded that Ruffed Grouse "answer drumming sounds" of nearby birds, and that the number of wing strokes and the duration of each drum were variable for an individual bird. In our study of the drums of Ruffed Grouse, we were interested particularly to learn if individuals were recognizable by their drumming.

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development has caused marked changes in the skull of the woodcock, especially the relation of the bones of the skull to the orbit, and to the foramen magnum. The unique osteology has been described by Shufeldt (1903). Hofer (1952, 1954) has recently made careful studies of the skulls of various birds and describes two main types, the extended and the bent. He uses three axes: the axis of the bill, that of the base of the skull, and that of the brain. In the extended type of skull, these three are nearly parallel, and close together. In the bent type of skull they may make marked angles with each other. The cormorant is an example of the former; most birds are of the bent type; Hofer gives examples in his figures of parrot, hawk, pigeon and four of the snipe family, including Scolopax, which is the extreme of the bent type. No measurements of the angles are recorded. The extraordinary position of the woodcock's brain within the skull, and its relation to eye and bill was brought forcibly to my attention the first time I removed the brain. It seemed to be almost upside-down with the cerebellum in a ventral position and the medulla oblongata leaving the cranial cavity through a ventrally placed foramen magnum with a slightly frontal slant (see Fig. 1). MATERIAL AND METHOD In order to follow through on this preliminary observation, two more woodcock, a Short-billed Dowitcher, a Semipalmated Sandpiper, a Semipalmated Plover, and three Herring Gulls were collected. Dissections were made of formalin fixed specimens. It was found that good fixation of the brain in situ could be obtained by skinning the head and neck immediately after death, removing the eyes, and then placing the whole head in 20% formalin for 10 days. After a thorough washing the dissection could be carried out using "magnifocuser" eye-glasses and small surgical rongeurs.