Sexual Dimorphism and Food Habits in Three North American Accipiters
Sexual Dimorphism and Food Habits in Three North American Accipiters
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三种北美鹰的性别二态性和食物习惯
DOI：
10.2307/4083053
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发表时间：
1966
期刊：
影响因子：
--
通讯作者：
R. W. Storer
中科院分区：
文献类型：
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作者：
R. W. Storer
三种分布广泛的北美鹰，尖胫鹰（Accipiter striatus velox），库珀的鹰（A。cooperii）和Goshawk（A. Genomalatricapillus）在大小上差异很大。在对这三种鹰的体重、翅膀面积和骨骼比例进行研究的过程中（Storer，1955），很明显，尽管这三种鹰的雌性平均比雄性大，但在最小的鹰（Sharp-shinned Hawk）中，体型上的性别差异最大，而在最大的鹰（Goshawk）中，性别差异最小。为了更精确地确定这三个物种的两性异形程度，我测量了密歇根大学动物学博物馆收藏的研究皮肤的翅长（弧）。使用的系列足够大，以提供一个很好的估计物种内的变化和准确的平均值。所有测量的鸟类都是成年羽毛，并在北达科他州最东部的格拉夫顿和加拿大安大略的皮利角之间的地区收集。尖胫鹰的样本完全由密歇根州的鸟类组成;其他物种的样本包括来自大部分更广泛地区的鸟类。性别错误的鹰雀，尤其是苍鹰雀，在采集中似乎并不罕见，我强烈怀疑，一些性别错误的标本导致弗里德曼（1950：150-152）和其他人可能将测量和羽毛的变化描述为重叠，而不是实际情况。大部分的错误性别可能是由于收集者误将成对的卵巢（通常在本属鸟类中）当作睾丸。在我们的收藏中，四个苍鹰性别作为男性的收集者测量348，357，360和361毫米的翅膀长度。所有这些都是在冬季（12月至2月），当性腺很小，都有沉重的黑色条纹下部分，这通常是在成年女性。第五个苍鹰，性别作为一个女性，措施324毫米的翅膀长度，具有良好的barring-characteristic成年男性，并没有沉重的黑色条纹。这五种鸟被从样本中排除，即使如此，苍鹰的两个性别组的变异系数比其他物种的变异系数大10%以上（表1）。一只库珀鹰的性别被确定为雄性，但其翅长为261毫米，上部羽毛呈褐色，这是成年雌性的特征，也被从数据中删除。测量数据总结在表1和表2中。根据男性和女性平均值之间的差异以及
THE three widespread North American bird hawks, the Sharp-shinned Hawk (Accipiter striatus velox), Cooper's Hawk (A. cooperii), and the Goshawk (A. gentilis atricapillus) differ greatly in size. In the course of studies on weight, wing area, and skeletal proportions of these three species (Storer, 1955), it became apparent that although the females of all three species average larger than the males, the sexual difference in size was greatest in the smallest species, the Sharp-shinned Hawk, and least in the largest species, the Goshawk. To determine more precisely the degree of sexual dimorphism in these three species, I measured the wing length (arc) of study skins in the collection of The University of Michigan Museum of Zoology. The series used were large enough to provide both a good estimate of variation within the species and an accurate mean. All birds measured were in adult plumage and were collected in the region between Grafton, in extreme eastern North Dakota, and Point Pelee, Ontario, Canada. The sample of the Sharp-shinned Hawk consisted entirely of birds taken in Michigan; those of the other species included birds from most of the broader area. Mis-sexed accipiters, especially Goshawks, appear to be not infrequent in collections, and I strongly suspect that a few mis-sexed specimens have led Friedmann (1950: 150-152) and possibly others to describe the variation both in measurements and plumage as overlapping more than actually will be found to be the case. Much of the mis-sexing probably results from the collectors' mistaking the paired ovaries (usual in birds of this genus) for testes. In our collections, four Goshawks sexed as males by the collectors measure 348, 357, 360, and 361 mm in wing length. All were taken in the winter months (December to February) when the gonads are small, and all have the heavy black streaking on the under parts, which is usually found in adult females. A fifth Goshawk, sexed as a female, measures 324 mm in wing length, has the fine barring characteristic of adult males, and lacks heavy black streaking. These five birds were omitted from the samples, and even so the coefficient of variation is over 10 per cent larger for both sex groups of the Goshawk thlan for those of the other species (Table 1). A Cooper's Hawk sexed as a male but measuring 261 mm in wing length and having the brownish plumage of the upper parts characteristic of adult females was also omitted from the data. The measurement data are summarized in Tables 1 and 2. Judging froim the difference between the means for males and for females and from