232 SHORT COMMUNICATIONS

Condor, 82:232-233 @ The Cooper Ornithological Society 1980

DIETS OF YOUNG LAPLAND TABLE 1. Prey items obtained from young Lapland LONGSPURS IN ARCTIC Longspurs. ’ AND SUBARCTIC ALASKA BXIOW Old Chevak (1975) (1976)

%of % of T. Il. SEASTEDT taxa Number biomass Number biomass

Tipulu curinifrons Extensive data are available on the breeding biology larvae 12 6.2 0 0 of Lapland Longspurs (Calcarius Zapponicus) nesting pupae 95 36.9 1 0.1 in arctic tundra near Barrow, Alaska (Custer and Pi- adults 48 15.6 8 1.3 telka 1977, 1978, Seastedt and MacLean 1979). Those Prionocera spp. studies emphasized the close relationship between larvae 0 0 13 5.2 nesting chronology and the availability of food re- 0 0 31 10.1 sources, especially those provided by the crane , pupae adults 17 6.9 258 76.2 Tipula curini&ons. Custer and Pitelka (1977) suggest- ed that reproductive success at Barrow was contingent Pediciu hunnui upon fledglings reaching self-sufficiency before the larvae 5 0.5 0 0 end of the brief period of adult abundance. adults 66 2.4 9 0.1 Here, I compare the nestling and fledgling diet of Lap- land Longspurs at Barrow with data obtained from a Tenthredinidae subarctic site. Differences in diet suggest a difference larvae 81 10.2 0 0 in preferred feeding habitat and a change in the timing adults 140 4.7 3 0.1 of nesting with respect to adult crane fly emergence. Small The subarctic site was located at Old Chevak (midges) 978 4.8 516 2.3 (61”26N,’ 165”27W)’ within the Clarence Rhode Na- tional Wildlife Refuge on the delta of the Yukon and Muscoid 285 5.3 13 0.1 Kuskokwim rivers. The site differed markedly from the Araneida (spiders) Barrow area: lowland areas were more sparsely vege- Linyphiidae 122 4.7 1 0.0 tated and subjected to spring tides; upland tundra con- Lycosidae 0 0 24 3.1 sisted of large, contiguous areas of mosses and lichens, and discrete ice-wedge polygons were absent. Vege- Others 33 1.8 8 1.4 tation of the Old Chevak area has been described by TOTAL 1,882. 100.0 885 100.0 Mickelson (1975); Holmes (1970) obtained climatic ’ Arthropod weights are reported in Custer and Pitelka (1978) and Seas- data 16 km north of the present subarctic study site. tedt and MacLean (1979). Prey items fed to nestlings and fledglings were col- lected with the pipe-cleaner ligature method (Hussell 1972). Attempts to obtain food items from nestlings less than four days old were largely unsuccessful. Young life form of the prey. Adult crane flies composed 36% longspurs leave the nest when they are about eight of the total crane fly biomass at Barrow, whereas they days old but remain flightless until about day 12 (Mah- composed 83% of the total at Old Chevak. Adult crane er 1964). Therefore, wire mesh enclosures were used flies became the dominant prey of the nestling diet at to contain fledglings during this interval. Samples were Old Chevak on 15 June, four days after the first eggs obtained from five nests at each site. Data obtained hatched. Adult crane flies at Barrow dominated the diet from the Old Chevak area, collected between 11 June after 11 July, 16 days after the first eggs hatched. Little and 1 July 1976, were compared with those reported variation has been reported in the mean dates of crane from Barrow by Seastedt and MacLean (1979), collect- fly emergence at Barrow (MacLean and Pitelka 1971), ed between 25 June and 20 July 1975. and the nesting chronology of longspurs at Barrow ap- Over 90% of the biomass of the nestling and fledg- pears to be synchronized with crane fly pupation and ling diet at Old Chevak was composed of crane flies adult emergence (Custer and Pitelka 1977). (Prionocera spp.; Table 1). These species (I.’ parryi Data reported here are based on a single field season and P. n. sp.; G. W. Byers, University of Kansas, pers. at Old Chevak, and conclusions are tentative. How- comm. to S. F. MacLean, Jr.), are semi-aquatic crane ever, these findings can be interpreted on the basis of flies associated with wet, lowland habitats. In contrast, those data that are available on arthropod abundance the longspur diet at Barrow was dominated by Tip& in the subarctic, and on information regarding the abil- curinif~-ons, crane flies found primarily in mesic and ity of longspurs to exploit this resource. Holmes (1970) upland habitats (MacLean and Pitelka 1971, Clement reported that lowland areas were more productive in 1975). Sawflies (Tenthredinidae), found primarily on arthropod biomass than were uplands at his nearby willows in mesic areas, were of secondary importance subarctic site. High densities of upland crane fly at Barrow, but were nearly absent from the longspur species were not found in the subarctic. The opposite diet at Old Chevak. Other prey items of some impor- pattern is generally true at Barrow, and longspurs con- tance at one or both sites included another crane fly tinue to feed in mesic and upland areas even during (Pediciu hunnui), midges, muscoid flies and spiders. the occasional year when lowlands contain more crane Overall, the amount of diet overlap as measured by the flies (Seastedt and MacLean 1979). Custer and Pitelka percent of biomass shared in common at the two sites (1978) noted that the conical fringillid bill of longspurs was only 12.4%. restricts these birds to mostly surface feeding. Long- A second contrasting feature of the nestling and spurs may obtain Tip& larvae and pupae by searching fledgling diets at the two sites was the difference in and picking through mosses and lichens; however, SHORT COMMUNICATIONS 233 they appear unable to probe wet areas for Prionoceru LITERATURE CITED immatures. Lowlands at Old Chevak appeared more CLEMENT, L. E. 1975. The ecology of Tip& carini- sparsely vegetated than lowland meadows at Barrow, frons Holm (Diptera, Tipulidae) in the arctic and these subarctic lowlands may have been more ac- coastal tundra of northern Alaska. M.S. thesis, cessible to longspurs than those at Barrow. However, Univ. Alaska, Fairbanks. data reported in Table 1 indicate that birds obtained CUSTER, T. W., AND F. A. PITELKA. 1977. Demo- mostly adult prey. Subarctic crane fly larvae and pupae, graphic features of a Lapland Longspur population while abundant in lowlands, may be unavailable to near Barrow, Alaska. Auk 94:505-526. longspurs. Thus, in order to provide adequate food for CUSTER, T. W., AND F. A. PITELKA. 1978. Seasonal nestlings in the subarctic, egg laying may be delayed trends in summer diet of the Lapland Longspur in order to synchronize hatching with the emergence near Barrow, Alaska. Condor 80:295-301. of adult crane flies. No data are available on the diet HOLMES, R. T. 1970. Differences in population den- of young longspurs following fledging; however, the sity, territoriality and food supply of Dunlin on warmer and longer summer environment at Old Che- arctic and subarctic tundra, p. 303-320. In A. Wat- vak is likely to provide adequate food resources be- son [ed.], populations in relation to food yond the date when food becomes limited at Barrow. resources. Br. Ecol. Sot. Symp. 10. Blackwell Sci- Unlike Barrow, then, nesting probably can be delayed entific Publ., Oxford. without harming the survivorship of post-fledgling, HUSSELL, D. J. T. 1972. Factors affecting clutch size young longspurs. in arctic passerines. Ecol. Monogr. 42:317-364. MACLEAN, S. F. JR., AND F. A. PITELKA. 1971. Sea- sonal patterns of abundance of tundra SUMMARY near Barrow. Arctic 24: 1940. Diets of young Lapland Longspurs in arctic and sub- MAHER, W. J. 1964. Growth rate and development of arctic Alaska differed in species composition and the endothermy in the Snow Bunting (Plectrophenax proportion of diet represented by adult crane flies. nivalis) and Lapland Longspur (C&a&s Zappon- These findings suggest a difference in preferred feed- icus) at Barrow, Alaska. Ecology 45:520-528. ing habitat and a difference in the nesting chronology MICKELSON,P. G. 1975. Breeding biology of Cackling with respect to the emergence of adult crane flies. The Geese and associated species on the Yukon-Kus- pattern of resource abundance and the ability for long- kokwim Delta, Alaska. Wildl. Monogr. 45: l-35. spurs to exploit these resources are hypothesized as SEASTEDT,T. R., AND S. F. MACLEAN, JR. 1979. Ter- causal factors. ritory size and composition in relation to resource I thank S. F. MacLean, Jr. for numerous suggestions abundance in Lapland Longspurs breeding in arc- and contributions to the study. Brina Kessel and T. W. tic Alaska. Auk 96:131-142. Custer suggested improvements to the manuscript. The generosity and assistance of Don Frickie, C. P. Division of Life Sciences, University of Alaska, Fuir- and Carla Dau and C. M. Boise of the Clarence Rhode banks, Alaska. Present address: Institute of Ecology, National Wildlife Refuge, U.S. Fish and Wildlife Ser- University of Georgia, Athens, Georgia 30602. Ac- vice, are sincerely appreciated. cepted for publication 26 February 1980.