Repeated Observations of Northern Goshawks Foraging as Terrestrial Predators
Repeated Observations of Northern Goshawks Foraging as Terrestrial Predators
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多次观察到北方苍鹰作为陆地掠食者觅食
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发表时间：
2017
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通讯作者：
Robert A. Miller
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作者：
Robert A. Miller
北方大鹰(Accipiter gentilis；以下简称苍鹰)是一种多面手捕食者，占据着北极北部和温带的森林(Squires和Reynolds，1997)。苍鹰的饮食已经在许多地区得到了研究，而且在不同的研究地点有很大的不同，但一些鸟类和哺乳动物的属是一致的(Squires和Reynolds 1997，Squires和Kennedy 2006)。在北美北部的大盆地内，苍鹰的繁殖季节食物通常由贝尔丁地松鼠(Urocitellus beldingi，也称为Spermophilus beldingi；Young和Bechard，1994年，Miller等人)主导。2014年)。当地对带状地松鼠等野外捕食物种的依赖程度高于研究苍鹰饮食的其他地区(见Miller等人的摘要)。2014年)。这种差异可能是当地觅食行为变化的结果，也可能是培育或必要的。苍鹰被描述为坐着等待的捕食者(即伏击)和跳跃式捕食者(即栖息时搜索；Bloxton 2002，Squires和Kennedy 2006)。苍鹰最常在栖息地捕食，但偶尔也会在飞行时攻击(Kenward 1982)。苍鹰也通过沿着森林边缘快速飞行来捕食(Johnsgard 1990，Backstrom 1991)，并似乎根据植被特征改变它们的狩猎方式(Bloxton 2002)。一些猛禽物种以其陆地觅食和跟踪行为而闻名(例如，Caracara属物种；Sazima2007)。在地面上跟踪猎物可能在露天物种中更为普遍，如铁头鹰(Buteo regalis；Wakeley 1978)或哈里斯鹰(Parabuteo unicinctus；Bednarz 1988)，但一些露天物种似乎仍然喜欢从栖息地狩猎(例如红尾鹰[Buteo jamaicensis]；Janes 1984)。库珀鹰与苍鹰关系密切，通常更容易被观察到，众所周知，它偶尔会徒步追捕猎物(Curtis等人。2006)。只有一篇发表的参考文献详细描述了苍鹰作为陆地捕食者在地面上开始追捕猎物(Bergstrom，1985)。然而，Kenward(2006)警告说，报道的苍鹰觅食行为可能偏向于最明显的技术，而其他行为被低估了。在这里，我报告了反复观察到的苍鹰从地面上猎杀贝尔丁地松鼠，以类似于哺乳动物陆地捕食者的方式跟踪猎物。在2013年6月的第一周，我在爱达荷州南部的苏布利特山脉(北纬42.28-42.58，西经112.98-113.18)进行了苍鹰调查。每天晚上，我都会看到一只成年苍鹰在猎取长满鼠尾草的艾草(Artemisia spp.)我的营地前面的山坡(图1)。我观察到了对贝尔丁地松鼠的成功和失败的攻击，这些松鼠是从距离现场大约100米的栖息地上发射的。这一周有两次，我观察到一只苍鹰在地面上捕猎。每一次，苍鹰都从森林飞到山艾树覆盖的山坡的一端，然后栖息在那里。几分钟后，苍鹰低下头，开始在山艾丛中徘徊，绕过山坡上的灌木丛。两次狩猎都成功了，苍鹰带着一只地松鼠飞回了森林。在随后的每一年，2014年、2015年和2016年，我都观察到了类似的行为，尽管我不知道苍鹰是否是同一个人。我没有量化这一策略的成功程度，但观察到了成功和不成功的狩猎尝试。由于骚乱，一些尝试没有成功。至少有两次，穿越山坡的繁忙道路上的车辆交通扰乱了狩猎，有一次，一只红尾鹰冲走了苍鹰，把它追回了森林。在2011年和2012年繁殖季节，在我报告观察之前，我在西边的卡西亚山脉(当地称为南山)进行苍鹰猎物调查(北纬42.08-42.38，西经114.08-114.48；Miller等人)。2014年)。至少有三次，我出人意料地把一只成年苍鹰从一片没有森林的土地上冲了出来。每一次都发生在以山艾树和互补灌木为主的景观中，距离森林0.100米。尽管我有一个电子邮件地址：robertMiller7@boisestate.edu
The Northern Goshawk (Accipiter gentilis; hereafter goshawk) is a generalist predator occupying boreal and temperate forests of the Holarctic (Squires and Reynolds 1997). The diet of goshawks has been studied in many areas and varies substantially among study sites, but some avian and mammalian genera are consistently represented (Squires and Reynolds 1997, Squires and Kennedy 2006). Within the northern Great Basin of North America, the breeding-season diet of goshawks is often dominated by Belding’s ground squirrels (Urocitellus beldingi, also known as Spermophilus beldingi; Younk and Bechard 1994, Miller et al. 2014). The local reliance upon an open-country prey species such as the Belding’s ground squirrel is higher than in other locations where goshawk diet has been studied (see summary in Miller et al. 2014). This difference may be the result of, or may foster or necessitate variation in local foraging behavior. Goshawks have been described as sit-and-wait predators (i.e., ambush) and saltatory predators (i.e., searching while perched; Bloxton 2002, Squires and Kennedy 2006). Goshawks most often hunt from perches, but occasionally attack while on the wing (Kenward 1982). Goshawks also hunt by flying rapidly along forest edges (Johnsgard 1990, Backstrom 1991), and appear to modify their hunting styles based on vegetation characteristics (Bloxton 2002). Some raptor species are well known for their terrestrial foraging and stalking behavior (e.g., species within the genus Caracara; Sazima 2007). Stalking prey on the ground may be more prevalent among open-country species such as Ferruginous Hawks (Buteo regalis; Wakeley 1978) or Harris’s Hawks (Parabuteo unicinctus; Bednarz 1988), yet some open-country species still appear to favor hunting from perches (e.g., Red-tailed Hawks [Buteo jamaicensis]; Janes 1984). Cooper’s Hawks (Accipiter cooperii), closely related to the goshawk and generally more easily observed, are known to occasionally pursue prey on foot (Curtis et al. 2006). Only one published reference provides a detailed description of a goshawk initiating pursuit of prey on the ground as a terrestrial predator (Bergstrom 1985). However, Kenward (2006) cautions that reported observations of goshawk foraging behavior may be biased toward the most visible techniques, with other behaviors going underreported. Here, I report repeated observations of goshawks hunting Belding’s ground squirrels from the ground, stalking prey in a manner similar to that of mammalian terrestrial predators. During the first week of June 2013, I was performing goshawk surveys within the Sublett Mountains of southern Idaho (42.28–42.58N, 112.98–113.18W). Each evening, I observed an adult goshawk hunting the sagebrush-covered (Artemisia spp.) hillside in front of my camp (Fig. 1). I observed both successful and unsuccessful attacks on Belding’s ground squirrels launched from a perch approximately 100 m from the site. On two occasions during the week, I observed a goshawk hunting from the ground. In each instance, the goshawk flew from the forest to one end of the sagebrush-covered hillside, and perched there on the ground. After several minutes, the goshawk lowered its head and started stalking through the sagebrush, weaving around bushes across the hillside. On both occasions, the hunt was successful and the goshawk flew back into the forest with a ground squirrel. I observed similar behavior in each subsequent year, 2014, 2015, and 2016, although I do not know if the goshawk was the same individual. I have not quantified the success of this strategy, but have observed both successful and unsuccessful hunting attempts. Some attempts were unsuccessful because of disturbance. On at least two occasions, vehicle traffic on a busy road that crosses the hillside disrupted the hunting, and on one occasion a Red-tailed Hawk flushed the goshawk and chased it back into the forest. During the 2011 and 2012 breeding seasons, prior to my reported observations, I was performing goshawk prey surveys in the Cassia Mountains, known locally as the South Hills, to the west (42.08–42.38N, 114.08–114.48W; Miller et al. 2014). On at least three occasions, I unexpectedly flushed an adult goshawk from the ground in a nonforested landscape. Each instance occurred within a landscape dominated by sagebrush and complementary shrubs, at a distance .100 m from forest. Although I did 1 Email address: RobertMiller7@boisestate.edu