The Condor891169-174 0 The Cooper Ornithological Society 1987 MIGRATION AND MORTALITY OF ALBERTA FERRUGINOUS HAWKS JOSEFK. SCHMUTZ Department of Biology Universityof Saskatchewan,Saskatoon S7N 0 WO, Canada RICHARD W. FYFE Environment Canada, Canadian Wildhfe Service,4999-98 Avenue,Edmonton T6B 2X3, Canada Abstract. Since 1967, 2,444 FermginousHawks (Buteo regalis) have been bandedin southeasternAlberta and 80 recoveriesare examined.The majority of AlbertaFerruginous Hawkswinter in Texas.Upon departingfrom their grasslandbreeding range in September or October,they exhibit a strongtendency to remain in habitat broadly categorizedas grassland.As a result,the hawksmix little with the westerlypopulations frequenting desert shrubhabitat. While in Texas,Ferruginous Hawks are commonnear black-tailedprairie dog (Cynomysludovicianus) colonies regardless of the land use in the surroundingarea. Survivorshipschedules based on band returnssuggest that 66% of the hawksdie during their firstyear. Key words: FerruginousHawk; gene flow; migration;survivorship; grassland: winter ecol- INTRODUCTION and depart from their breeding range in Alberta Animals may move for many reasons including at a time when the Richardson’s ground squirrel finding food, finding mates, avoiding predators (Spermophilus richardsonii) are entering estiva- and becauseof aggressive interactions. Most an- tiomhibemation (Schmutz et al. 1979). imals disperseat least a short distance from their Although the migratory behavior of Ferrugi- natal to breeding site. Some also exhibit long nous Hawks has not been proven heritable, we distance migrations (see Swingland and Green- assumethat suchheritability exists and therefore wood 1983 for a review). Migration representsa that migration behavior can be influenced by nat- long distance movement followed by a return. ural selection. In this analysis we suggesta pat- The ultimate causeof migration is an avoidance tern of migration which we think is exhibited by of temporarily adverseecological conditions, but Alberta Ferruginous Hawks in general. Since we proximate factors(e.g., food supply, weather) may basethis analysis on reportsof hawks which were trigger the onset and small-scale direction of either dead, sick or injured, we assume that this movement. Migratory movements of most bird subset of individuals behaved in a way similar populations are highly consistent, suggestinga to those not reported. genetic basis to this behavior. Migratory rest- METHODS lessnesshas been shown to have a genetic basis (Berthold and Quemer 1981), and since migra- From 1967 to 1980, 1,9 15 Ferruginous Hawks tory restlessnessis positively correlated with dis- were banded under a permit held by R.W.F. and tance migrated, the latter is assumed to be her- from 1983 to 1985, 529 were banded under a itable also. permit held by J.K.S. The bands were applied In this paper we describe the migratory habit when the nestlings were more than half grown. of the Ferruginous Hawk (Buteo regalis) banded Most banding was done on a 3,000 km2 area in Alberta. This population inhabits the most southeastof Hanna, Alberta but somehawks were northern portion of this species’ range consisting banded throughout southeasternAlberta. Two of of sparsely treed grassland east of the Rocky 74 hawks recovered were banded in southwest- Mountains and south of parkland habitat. The em Saskatchewan. Once a report of a banded hawks rely largely on ground squirrels for prey hawk was received, a questionnaire was sent to the finder requesting additional information on precise location, habitat and condition of the ’ ’ Received2 1 May 1986.Final acceptance13 August hawk when found (freshly killed, partly decayed, 1986. fully decayed). [I691 170 JOSEF K. SCHMUTZ AND RICHARD W. FYFE 0 512 month, . 13-36 months : 0 s37 months :..: ../ :. .. FIGURE 1. Latitude and time of year of recoveries of Ferruginous Hawks. Dates for hawks reported as freshly killed were used directly. From 5 to 45 days dependingon location and time ofyear were subtracted from the finding date of eight hawks reported as partly decayed. To study their distribution on the winter range, J.K.S. counted Ferruginous Hawks and other raptors seen on a road transect in southwestern New Mexico and northern Texas. The route was from El Paso to Seminole, north around Ama- FIGURE 2. Locationofrecovered Ferruginous Hawks rillo and back to El Paso via Clovis and Roswell, is shown in relation to banding area and wintering range of this species.The solid line outlines the entire New Mexico. This count took place from 3 to 7 wintering rangeofthis speciesbased on 1,532 sightings November 1985. Hawk location, activity, hab- of FerruainousHawks during 37.172 hr of observation itat type, and land use were recorded. To mini- on Audibon ChristmasBird Co&s from 1980to 1983. mize a potential bias in visibility imposed by The brokenline denotesthe “concentrated”winter range and includes counts where more than one hawk was differences in vegetation or terrain, the search seen per 100 km travelled. In Mexico, Ferruginous was concentrated within 200 m of the road. A Hawks were seen on few counts totalling only 112 hr total of 246 raptors were recorded on 1,392 km of observation and hence a concentratedrange is not travelled. shown. The entire range shown there representssight- ings and recoveries combined. RESULTS AND DISCUSSION In someraptor populations, adults remain in their Young also appear to migrate on their own in breedingarea year-round and thesemay be joined Alberta. After fledging, during the secondhalf of by others from other areas (Mebs 1964). Some July and all of August 1985, 10 adults and 20 Ferruginous Hawks are present all year in the young were recorded on a study area south and southern part of their breeding range (Olendorff east of Hanna, Alberta, whereas only four adults 1973, Smith and Murphy 1978) but whether these and no young were seen in September and Oc- were migrants or summer residents was un- tober. One breeding pair was observed on what known. was presumed to be their previously used nest tree on 16 October 1985. One young of this pair TIMING OF MIGRATION was found partly decayedin Texas on 22 October In Alberta, apparently all individuals departed 1985. The locations of recoveries reported as from their northern part of the breeding range freshly killed or partly decayed also suggestthat by late October. Young which were marked in most young Ferruginous Hawks leave Alberta in Utah, departed independently of nest mates and August (Fig. 1). Later, during November through their parents (Woffinden and Murphy 1983). February only one (5%) of 19 individuals was FERRUGINOUS HAWK MIGRATION 171 found north of Colorado and Kansas. Few were TABLE 1. Number of Ferruginous Hawks recorded reported in March through June but the three on Audubon Christmas Bird Counts (American Birds) in 1980 to 1983. Only states with counts of one or adults, 36 months old or older, were found dis- more FerruginousHawks during at least 100 hr of ob- tinctly further north than four younger individ- servation over four years are included. The number of uals. This small sample suggeststhat subadults FerruginousHawks recovered are also given. do not return to their natal area or they spend Totaltime REOV- less time there than adults. Age at first breeding stateor CO”“tw (hr) cries is three years in this speciesbased on a sample of seven known-age adults livetrapped at nests. Kansas 15.0 568 3 Nebraska 7.5 227 6 Colorado 6.5 2,943 4 Wyoming 5.6 108 3 MIGRATION ROUTES New Mexico 5.4 1,821 1 Of 74 Ferruginous Hawks reported dead, 13 died Mexico 5.4 112 5 during the first four months of life within 150 Oklahoma 5.1 901 2 Nevada 4.9 143 km of their banding location. The remaining 6 1 Texas 4.9 5,624 15 locations are shown in Figure 2. The results in- Arizona 4.7 4.220 1 dicate that the migration route and winter dis- Utah 4.2 ‘708 tribution of Alberta Ferruginous Hawks are dis- Washington 3.7 164 tinctly nonrandom in comparison to the total South Dakota 3.2 407 4 California 2.9 18,530 population. While Ferruginous Hawks can be Oregon 2.0 298 found wintering anywhere in the western U.S., Montana 1.8 164 2 Alberta hawks occupied only the midwestern Missouri 1.4 144 statesand most wintered in Texas. On Audubon Christmas Bird Counts (American Birds 1980 to 1983), Ferruginous Hawks were more abundant natural selectionwas operating on Alberta hawks south of about 43”N latitude. The pattern was to cause a change in the areas used. corroborated by a preponderance of Alberta To further compare the east-westdistribution hawks recovered south of Wyoming and South of recoveries of Ferruginous Hawks banded in Dakota during November through February. North Dakota (Gilmer et al. 1985) with those of Thus, while those from Alberta segregatethem- this study we considered all recoveries south of selves from the remainder of the wintering pop- Wyoming (41”N latitude). Of 22 recoveries of ulation further west, their distribution north and North Dakota hawks, 11 (50%) were west of a south more closely reflectsthat of the population line extending the eastern boundary of the Texas as a whole. The preponderance of Alberta hawks Panhandle (1Oo”W longitude). Of 42 hawks orig- in the midwestem statesin winter doesnot mere- inating from Alberta, 38 (9 1O/o) were recovered ly reflect east-westdifferences in abundance. Fer- west of 1OO”Wlongitude (x2 = 13.18, P < 0.001). ruginous Hawks were common in California but Therefore,North Dakota hawkswere more widely no individuals banded during this study were scatteredeast and west than Alberta hawks and found there (Table 1). Only six Ferruginous the latter overlap in significant numbers only with Hawks were reported from northern Mexico. Our the western segment of the North Dakota pop- data may underestimate the importance of this ulation. Alberta hawks, which have a more region as a wintering area becausereporting rates northerly origin, do not “leap-frog” on migration may differ.