SHORT COMMUNICATIONS 273

Strix use buildings, especially barns, as nest HOUSTON, C. S. 1959. First records of the Barred sites. The ( &co) uses build- in Saskatchewan. Blue Jay 17:94. HOUSTON, C. S. 1961. First Saskatchewan nest of ings as nest sites 15% of the time, similarly, . Blue Jay 19:114-l 15. the (Strix urulensis) nests in build- JOHNSON,D. H. AND D. G. FOLLEN. 1984. Barred ings 2-4% of the time (Mikkola 1983). and nest boxes. Raptor Res. 18:34-35. MAZUR, K. M., I? C. JAMES, AND S. D. FRITH. 1997. ACKNOWLEDGMENTS Barred Owl (Strix maria) nest site characteristics I thank M. Belcher, J. S. Marks, J. E Roy, and four in the boreal of Saskatchewan, Canada. U.S. anonymous reviewers for constructive criticism. Forest Service General Technical Report NC-190: 267-27 1. LITERATURE CITED MIKKOLA, H. 1983. Owls of Europe. Buteo Books, BENT, A. C. 1938. Life histories of North American Vermillion, South Dakota. of prey. U.S. Nat. Mus. Bull. 170:182-201.

Wilson Bull., 11 l(2), 1999, pp. 273-276

Double Brooding in the Long-eared Owl

Jeffrey S. Marks,2’ and Alison E. H. Perkins ’

ABSTRACT.-Owls in the family Strigidae typi- fecundity of the adults and their young from cally raise no more than one brood per year. We doc- the first brood. The occurrence of double umented what apparently is the first unequivocal case brooding may be influenced by factors such of double brooding in Long-eared Owls (Ash otus). A as length of the breeding season, food avail- banded female raised 12 young in two nesting attempts compared with a mean of 5.3 young for three single- ability, growth rates of the young, and the du- brooded females that nested in the same grove. Two ration and quality of parental care (e.g., Drent factors may have influenced the occurrence of double and Daan 1980, Askenmo and Unger 1986, brooding: the first nest was initiated unusually early in Tinbergen and van Balen 1988). the year (mid-February) and food availability (in the Double brooding is relatively rare in rap- form of ) was high. The rare description of double tors, presumably because the length of the brooding in Long-eared Owls may be due to the dif- ficulty of detecting it. Alternatively, double brooding breeding cycle and extended postfledging care may be uncommon because it is seldom an economi- preclude its occurrence (Newton 1979, Mor- cally viable strategy. Factors that would select against rison 1998). Among nocturnal raptors, double double brooding include low probability of recruitment brooding occurs regularly in Barn Owls ( of the first-brood young, and reduced survival and fe- alba; Marti 1992, 1997) and occasionally in cundity of the adults. Received17 Sept. 1998, accepted Florida Burrowing Owls (Athene cuniczhria 29 Dec. 1998. JEoridunu; Millsap and Bear 1990) and Boreal Owls ( funereus; Kellom&i et al. 1977, Solheim 1983). During a study of The number of young raised per year is an breeding Long-eared Owls (Ask otus), we important component of an individuals’ life- documented a female that raised two broods time reproductive success. Double brooding, during the same nesting season. Here, we de- in which a second brood is attempted after a scribe the event and discuss factors that may successful first attempt, is a viable strategy if have influenced its occurrence. the increase in fitness that results outweighs the cost of any reduction in future survival or STUDY AREA AND METHODS

The study area is a small grove (ca 2 ha) of quaking ’ ’ Montana Cooperative Wildlife Research Unit, ( tremuloides) and black hawthorns Univ. of Montana, Missoula, MT 59812. (Crataegus douglasii) located about 16 km west of Z Corresponding author; Poison, Lake County, Montana (47” 40’ N, 114” 20’ E-mail: [email protected] W). The elevation at the site is 888 m, and the nesting 274 THE WILSON BULLETIN l Vol. 111, No. 2, June 1999 grove is surrounded by grasslands and agricultural note her pattern of flight-feather molt that we fields (mostly hay). The 11 Long-eared Owl nests that had confirmed in the hand the previous night occurred in the grove in 1997 and 1998 were in old (4 primaries and 2 secondaries growing on nests of Black-billed Magpies (Pica pica) and Amer- ican Crows (Corvus bruchyrhynchos). each wing). Also at this time, we noticed that Adults were captured at night in mist nests placed her mate was banded. After several attempts, near the nest or at dusk with the aid of a plastic decoy we succeeded in capturing the male on the of a Great (Bubo virginianus). Captured evening of 13 July, at which time the oldest adults were classified as after hatching year (AHY) or chicks were capable of short flights from tree after second year (ASY) based on the absence or pres- to tree. The male proved to be no. 914, the ence of two generations of secondaries, respectively same male that had nested at this site in 1997. (see Pyle 1997). During the breeding season, the sex of most adults can be determined in the field by dif- Female 951 was still present, and both adults ferences in plumage coloration and in the hand by presumably were provisioning their fledglings. presence or absence of an incubation patch (Marks et Interestingly, male 914 had not started flight- al. 1994). feather molt. Female 951 fledged 12 young (defining RESULTS “fledging” as capable of sustained flight; On 16 February 1998, we observed a fe- Marks 1986) in two nesting attempts com- male Long-eared Owl incubating at a nest pared with a mean of 5.3 young (range 5 to (PSNII) about 25 m north of a nest that had 6) produced by the other three pairs that nest- produced young the previous year. The male ed in the grove in 1998. The estimated time was roosting nearby, but we could not deter- between the initiation of 95 ls’ two nesting at- mine whether he was banded. Three of the tempts was 90 days (i.e., 12 February and 12 five Long-eared Owl nests that occurred in the May). At the time 951 initiated her second grove in 1998 were initiated in February; clutch, the oldest offspring from her first PSNII appeared to be the earliest of these brood would have been about 6 weeks old. nests. On 2 April, JSM captured the adult (AHY) female (band no. 951) by hand at DISCUSSION PSNII as she was brooding seven young that Several records of double brooding by ranged in age from about 1 to 3 weeks old. Long-eared Owls have been reported in Eu- Based on the estimated age of the chicks and rope (Reinsch and Wamcke 1968, Rinne 1981, an incubation period of 28 days (Marks et al. Scott 1997), but in each case the evidence was 1994), female 951 would have initiated egg circumstantial. To our knowledge, ours is the laying on 12 February, and the oldest chick first report of double brooding in Long-eared would have hatched on 12 March. Other du- Owls based on a banded individual. ties prevented us from catching the mate of We suspect that weather and food avail- female 951 during this nesting attempt. ability played a major role in this case of dou- During a visit to the nesting grove on 25 ble brooding. The winter of 1998 was unusu- June, we found a new Long-eared Owl nest at ally mild in western Montana. The ground at the northern edge of the grove 28 m from nest the study area was virtually free of from PSNII. A female was brooding small chicks January onward (pers. obs.), and the mean that appeared to be about 2 weeks old, and a temperature in February was 2.1” C above male was flushed from the same roost site typ- normal at the Kerr Dam weather station 13 km ically used by the PSNII male earlier that from the study area (data obtained from the spring. We returned to the nest on the evening National Climatic Data Center). In addition, of 30 June and captured the female in a mist voles ( spp.) were abundant in winter net placed directly in front of the nest. She and spring; we saw many during the day, and proved to be 951, the same female that had other -eating raptors [i.e., Northern Har- fledged seven chicks earlier in the spring. The rier (Circus cyaneus), Rough-legged Hawk next morning we banded her five chicks, (Buteo Zagopus), and Short-eared Owl (Ado which were about 2 to 3 weeks old. Female jkzmmeus)] were numerous in the study area. 951 was very aggressive as we handled her The mild weather and abundant food probably chicks, diving and perching within 1 m of us induced Long-eared Owls to nest in February, and enabling us to observe her band and to which is very early for this (see Marks SHORT COMMUNICATIONS 275 et al. 1994). The continued high numbers of received a normal amount of parental care (the voles in summer provided an opportunity for second clutch was started when the oldest double brooding, at least for one of the three chicks from the first nest were 6 weeks old) pairs that began nesting in February. only if the female changed mates between In general, the incidence of second nesting nesting attempts (and the male continued to attempts in facultatively double-brooded spe- care for the young), or if one or both parents cies is negatively correlated with the laying continued to provision the first brood while date of the first clutch (e.g., Smith et al. 1987, starting the second (an unlikely occurrence Geupel and DeSante 1990, Morrison 1998). given that the male must provide food to the Our case agrees with this finding, but it raises incubating female). Moreover, the timing of the question of why the other two Long-eared second broods could interfere with the molt Owl pairs that nested early did not raise a sec- schedule of adults. Long-eared Owls generally ond brood. One possibility is that the pheno- begin molting in early June soon after breed- typic quality of the double-brooded pair was ing (Marks et al. 1994). The male attending high relative to the other pairs (see Verboven the second brood had not started flight-feather and Verhulst 1996). Although we have no ob- molt in mid-July, suggesting that his molt was jective measure of phenotypic quality in the delayed because of the late breeding effort. Long-eared Owls we studied, we note that the Delayed molt potentially could influence sur- male of the second nesting attempt had bred vivorship and fecundity (see Pietitiinen et al. successfully at the site in the previous year 1984, KjellCn 1994). (the other males did not breed there in 1997), In conclusion, double brooding appears to and the female that nested twice was in good be rare in Long-eared Owls, and it probably physical condition and was unusually aggres- occurs only when first nests are initiated early sive. Indeed, during her first attempt she at- and food availability is high. Nothing is tacked JSM when he entered the nest. More- known about how double brooding affects re- over, the ratio of her body mass (g) to wing cruitment of young from first versus second length (mm) at first capture (1.33) was higher broods, or whether it affects the survivorship than that of all but one of the other eight fe- and future fecundity of the parents. Whether males captured late in the brooding-rearing double brooding is a viable strategy in Long- period in 1997 and 1998 (2 = 1.11 ? 0.13 eared Owls remains to be determined from ad- SD, range 0.98-l .34). The local experience of ditional research. the male and the physical condition and ag- gressiveness of the female are consistent with ACKNOWLEDGMENTS the notion that they were high-quality individ- We thank P and D. Smith for granting access to their uals relative to the other early nesters in the land; C. Olson, T Dial, and R. Petty for help in catch- grove. ing owls; C. Marti for comments on the manuscript; Double brooding in Long-eared Owls may and H. Wright for translating two papers. This research be more common than previously thought. Al- was supported by a grant from the University of Mon- ternatively, it may indeed be rare because it is tana Research and Creativity Committee. seldom an economically viable strategy. For instance, the fitness gain from double brood- LITERATURE CITED ing would be marginal if the probability of ASKENMO, C. AND U. UNGEK. 1986. How to be double- recruitment of first-brood young is low (i.e., brooded: trends and timing of breeding perfor- because of reduced care from parents that di- mance in the Rock Pipit. Ornis Stand. 17:237- rect their efforts to a new brood), or if future 244. survival and fecundity of the adults are re- DRENT, R. H. AND S. DAAN. 1980. The prudent parent: duced. Female Long-eared Owls in Idaho de- energetic adjustments in avian breeding. Ardea serted their broods when the young were 6.5 68:225-252. GEUPEL, G. R. AND D. E DESANTE. 1990. Incidence to 8 weeks old, and males continued to care and determinants of double brooding in Wrentits. for the young until they were 8.5 to 11 weeks Condor 92:67-75. old (Ulmschneider 1990). If parental care of KELLOM.&KI, E., E. HEINONEN, AND H. TIAINEN. 1977. this duration is typical in Long-eared Owls, Two successful nestings of Tengmalm’s Owl in then the first of the two broods would have one summer. Ornis Fenn. 54: 134-135. 276 THE WILSON BULLETIN * Vol. I I I, No. 2, June 1999

KJELLBN, N. 1994. Moult in relation to migration in Owl Strix uralensis. Ann. Zool. Fenn. 21:277- birds: a review. Omis Svecica 4: l-24. 281. MARKS, J. S. 1986. Nest site characteristics and re- PYLE, I? 1997. Flight-feather molt patterns and age in productive success of Long-eared Owls in south- North American owls. Am. Birding Assoc. Mon- western Idaho. Wilson Bull. 98:547-560. ogr. Field Omithol. 2: l-32. MARKS, J. S., D. L. EV,ANS, AND D. W. HOLT. 1994. REINSCH, A. AND K. WARNCKE. 1968. Zweibruten bei Long-eared Owl (Ash otus). In The birds of North der Waldohreule. Anz. Ornithol. Ges. Bayern 8: America. No. 133 (A. Poole and E Gill, Eds.). 400-401. Academy of Natural Sciences, Philadelphia, Penn- RINNE, U. 1981. Beitrag zur Brutbiologie der Waldoh- sylvania; American Ornithologists’ Union, Wash- reule (Ash otus). Ornithol. Mitt. 33:62-65. ington, D.C. SCOTT, D. 1997. The Long-eared Owl. The Hawk and MARTI, C. D. 1992. (Tyto a&a). In The Owl Trust, London, U.K. birds of , no. 1 (A. Poole, P Stet- SMITH, H. G., H. K.&LLANDER, AND J.-A. NILSSON. tenheim, and E Gill, Eds.). Academy of Natural 1987. Effect of experimentally altered brood size Sciences, Philadelphia, Pennsylvania; American on frequency and timing of second clutches in the Ornithologists’ Union, Washington, D.C. Great . Auk 104:700-706. MARTI, C. D. 1997. Lifetime reproductive success in SOLHEIM, R. 1983. Bigyny and biandry in the Teng- Barn Owls near the limit of the species’ range. malm’s Owl Aegolius funereus. Ornis Stand. 14: Auk 114:581-592. 5 l-57. MILLSAP, B. A. AND C. BEAR. 1990. Double-brooding TINBERGEN, J. M. AND J. H. VAN BALEN. 1988. Food by Florida Burrowing Owls. Wilson Bull. 102: and multiple breeding. Acta Congr. Int. Ornithol. 313-317. 19:380-391. MORRISON, J. L. 1998. Effects of double brooding on ULMSCHNEIDER,H. 1990. Post-nesting ecology of the productivity of Crested Caracaras. Auk 115:979- Long-eared Owl (Asia otus) in southwestern Ida- 987. ho. M.S. thesis, Boise State Univ., Boise, Idaho. NEWTON, I. 1979. Population ecology of raptors. Bu- VERBOVEN, N. AND S. VERHULST. 1996. Seasonal vat- teo Books, Vermillion, South Dakota. iation in the incidence of double broods: the date PIETI&NEN, H., I? SAUROLA, AND H. KOLUNEN. 1984. hypothesis fits better than the quality hypothesis. The reproductive constraints on moult in the Ural J. Anim. Ecol. 65:264-273.

Wilson Bull., 111(2), 1999, pp. 276-278

Planning to Facilitate Caching: Possible Suet Cutting by a

Bernd Heinrich ’

ABSTRACT.-Many species of birds feed on suet The Common Raven, Corvus corn, is a in winter. As far as is known, they all take bite-sized feeding generalist (Bent 1946, Ratcliffe 1997). chunks by pecking into this food randomly and/or they Ravens feed on carrion (Ewins et al. 1986), tear off protruding pieces. I compared the peck-marks left on suet by Blue Jays (Cyanocitza cristata) and fruit, grain, eggs, and “garbage” (Nelson American Crows (Corv~ls brachyrhynchos) with those 1934, Marquiss and Booth 1986, Engel and left by Common Ravens (Corvus corax). Although Young 1989). Ravens also capture , most ravens feed like jays and crows, at least one in- , , , small , dividual made distinct grooves, aligning dozens of and other birds (Marr and Knight 1982, Camp consecutive pecks, apparently to cut transportable chunks off large suet blocks. Received 28 Aug. 1998, et al. 1993). I here describe a raven removing accepted 7 Jan. 1999. fat from a chunk of suet in an unusual or ab- errant way that differs markedly from the method used by jays, crows, and most other ravens. Chunks of beef suet that were either of suf- ’ Dept. of Biology, Univ. of Vermont, Burlington, ficient size so that they could not be carried VT 05405. off or that were nailed onto the frozen ground