Summary
Food samples of breeding Kestrels (Falco tinnunculus) and Long-eared Owls (Asio otus) were collected in the peak and low phase of their preferred prey (Microtus voles) in western Finland. Diets of pairs that bred as neighbours (≤1 km) with interspecifics were compared with those of non-neighbours. In both species, neighbouring pairs fed less on Microtus voles and more on alternative prey than did non-neighbours. Competition theory predicts that diet overlap should be lower during prey shortage and that diet similarity should be especially reduced in neighbouring pairs. Observations were consistent with expectations: diet similarity was lower in the low vole years and neighbouring pairs showed less diet overlap that non-neighbours. Differences in habitat composition and prey availability at the sample sites should not confuse the results. In addition to the high diet similarity, hunting habitats and nest sites of the species overlapped almost completely; they only showed clear temporal segregation in hunting. Probably because of food competition, the neighbouring pairs of both species produced significantly fewer young than the non-neighbours. These results contrast with the view that the diet composition and dietary shift of rodent-feeding predatory birds can be interpreted in terms of simple opportunistic foraging. In the breeding season, interspecific competition for food seems to be an important factor that affects the niches of these species, especially in northern areas, where the seasonal low phase of voles in spring and the number of alternative prey are lower than in more southern areas.
Similar content being viewed by others
References
Abrams P (1983) The theory of limiting similarity. Ann Rev Ecol Syst 14:359–376
Alatalo RV (1981) Competition in tits Parus spp. and the Goldcrest Regulus regulus: foraging shifts in multispecific flocks. Oikos 37:335–344
Alatalo RV, Gustafsson K, Lundberg A, Ulfstrand S (1985) Habitat shift of the Willow Tit Parus montanus in the absence of the Marsh Tit Parus palustris. Ornis Scand 16:121–128
Avery RA (1971) Estimates of food consumption by the lizard Lacerta vivipara Jacquin. J Anim Ecol 40:351–366
Beusekom CF van (1972) Ecological isolation with respects to food between Sparrowhawk and Goshawk. Ardea 60:72–96
Carothers JH, Jaksié FM (1984) Time as a niche difference: the role of interference competition. Oikos 42:403–406
Charnov EL, Orians GH, Hyatt K (1976) Ecological implications of resource depression. Am Nat 110:247–259
Cody ML (1974) Competition and the structure of bird communities. Princeton University Press, Princeton
Colwell RK, Futuyma DJ (1971) On the measurement of niche breadth and overlap. Ecology 52:567–576
Connell JH (1983) On the prevalence and relative importance of interspecific competition: evidence from field experiments. Am Nat 122:661–696
Craighead JJ, Craighead FC (1969) Hawks, owls and wildlife. Dover Publ, New York, 2nd Edition
Diamond JM (1978) Niche shifts and the rediscovery of interspecific competition. Am Sci 66:322–331
Emlen JM (1966) The role of time and energy in food preference. Am Nat 100:611–617
Erlinge S, Göransson G, Högstedt G, Liberg O, Loman J, Nilsson I, Nilsson T, von Schantz T, Sylvén M (1982) Factors limiting numbers of vertebrate predators in a predator prey community. Trans Intern Congr Game Biol 14:261–268
Forsman D (1984) Rovfagelsguiden. Lintutieto, Helsinki
Glutz von Blotzheim UN, Bauer KM (1980) Handbuch der Vögel Mitteleuropas. Band 9. Akademische Verlagsgesellschaft; Wiesbaden
Greene HW, Jaksié FM (1983) Food-niche relationships among sympatric predators: effects of level of prey identification. Oikos 40:151–154
Grossman ML, Hamlet J (1964) Birds of Prey of the World. Bonanza Books, New York
Gustafsson L (1985) Fitness factors in the Collared Flycatcher Ficedula albicollis Temm. Ph D thesis, Dept Zool, Univ Uppsala, Sweden
Haartman L von, Hildén O, Linkola P, Suomalainen P, Tenovuo R (1963–72) Pohjolan linnut värikuvin. Otava, Helsinki
Hairston NG, Smith FE, Slobodkin LB (1960) Community structure, population control, and competition. Am Nat 94:421–425
Herrera CM, Hiraldo F (1976) Food-niche and trophic relationships among European owls. Ornis Scand 7:29–41
Huey RP, Pianka ER, Egan ME, Coons LW (1974) Ecological shifts in sympatry: Kalahari fossorial lizards (Typhlosaurus). Ecology 55:304–316
Hutchinson GE (1957) Concluding remarks. Cold Spring Harbor Symp Quant Biol 22:415–427
Högstedt G (1980) Prediction and test of the effects of interspecific competition. Nature 283:64–66
Hämies J, Korpimäki E (1987) Insect food of the Kestrel, Falco tinnunculus, during breeding in western Finland. Aquilo Ser Zool 25 (in press)
Järvinen O (1977) A methodological note on the measurement of the diet specialization of predators. Ornis Fenn 54:90–91
Jaksić FM (1982) Inadequacy of activity time as a niche difference: the case of diurnal and nocturnal raptors. Oecologia (Berl) 52:171–175
Jaksié FM, Braker HE (1983) Food-niche relationships and guild structure of diurnal birds of prey: competition versus opportunism. Can J Zool 61:2230–2241
Korpimäki E (1981) On the ecology and biology of Tengmalm's Owl (Aegolius funereurs) in Southern Ostrobothnia and Suomenselkä, western Finland. Acta Univ Oul A 118 Biol 13:1–84
Korpimäki E (1982) Zur Aktivität des Stars (Sturnus vulgaris) in Süd-österbotten, Finnland, während der Nistzeit. Beitr Vogelkd (Jena) 28:129–138
Korpimäki E (1983) Tuulihaukkapönttökokeilun tuloksia. Lintumies 18:132–137
Korpimäki E (1984a) Population dynamics of birds of prey in relation to fluctuations in small mammal populations in western Finland. Ann Zool Fennici 21:287–293
Korpimäki E (1984b) Food piracy between European Kestrel and Short-eared Owl. Raptor Res 18:113–115
Korpimäki E (1985a) Prey choice strategies of the Kestrel Falco tinnunculus in relation to available small mammals and other finnish birds of prey. Ann Zool Fennici 22:91–104
Korpimäki E (1985b) Rapid tracking of microtine populations by their avian predators: possible evidence for stabilizing predation. Oikos 45:281–284
Korpimäki E (1985c) Diet of the Kestrel Falco tinnunculus in the breeding season. Ornis Fenn 62:130–137
Korpimäki E (1986) Predation causing synchronous decline phases in microtine and shrew populations in western Finland. Oikos 46:124–127
Korpimäki E (1987) Timing of breeding of Tengmalm's Owl Aegolius funereus in relation to vole dynamics in western Finland. Ibis 129:58–68
Korpimäki E, Haapoja R, Ikola S (1979) Two nests of the Kestrel close to each other. Lintumies 14:35
Korpimäki E, Huhtala K (1986) Nest visit frequencies and activity patterns of Ural Owls Strix uralensis. Ornis Fenn 63:42–46
Lack D (1946) Competition for food by birds of prey. J Anim Ecol 15:123–129
Lawlor LR (1980) Overlap, similarity, and competition coefficients. Ecology 61:245–251
Levins R (1968) Evolution in changing environments. Princeton Univ Press, Princeton
Lundberg A (1979) Residency, migration and a compromise: adaptations to nest-site scarcity and food specialization in three Fennoscandian owl species. Oecologia (Berlin) 41:273–281
MacArthur RH, Levins R (1967) The limiting similarity, convergence, and divergence of coexisting species. Am Nat 101:377–385
Marks JS, Marti CD (1984) Feeding ecology of sympatric Barn Owls and Long-eared Owls in Idaho. Ornis Scand 15:135–143
May RM (1975) Some notes on measuring the competition matrix, α. Ecology 56:737–741
Menge BA, Sutherland JP (1976) Species diversity gradients: synthesis of the roles of predation, competition, and temporal heterogeneity. Am Nat 110:351–369
Mikkola H (1983) Owls of Europe. T & AD Poyser, Calton
Minot EO (1981) Effects of interspecific competition for food in breeding Blue and Great Tits. J Anim Ecol 50:375–385
Newton I (1979) Population ecology of raptors. T & AD Poyser, Berkhamsted
Nilsson IN (1984) Prey weight, food overlap, and reproductive output of potentially competing Long-eared and Tawny Owls. Ornis Scand 15:176–182
Opdam P (1975) Inter- and intraspecific differentiation with respect to feeding ecology in two sympatric species of the genus Accipiter. Ardea 63:30–54
Pianka ER (1973) The structure of lizard communities. Ann Rev Ecol Syst 4:53–74
Piechocki R (1982) Der Turmfalke. Die Neue Brehm-Bücherie, A Ziemsen Verlag, Wittenberg Lutherstadt, 6.ed.
Pyke GH, Pulliam HR, Charnov EL (1977) Optimal foraging: a selective review of theory and tests. Quart Rev Biol 52:137–154
Reynolds RT, Meslow EC (1984) Partitioning of food and niche characteristics of coexisting Accipiter during breeding. Auk 101:761–779
Schmitt RJ, Coyer JA (1983) Variation in surfperch diets between allopatry and sympatry: circumstancial evidence for competition. Oecologia (Berlin) 58:402–410
Schmutz JK, Schmutz SM, Boag DA (1980) Coexistence of three species of hawks (Buteo spp) in the prairie-parkland ecotone. Can J Zool 58:1075–1089
Schoener TW (1971) Theory of feeding strategies. Ann Rev Ecol Syst 2:369–404
Schoener TW (1974) The compression hypothesis and temporal resource partitioning. Proc Natl Acad Sci US A 71:4169–4172
Schoener TW (1975) Presence and absence of habitat shift in some widespread lizard species. Ecol Monogr 45:233–258
Schoener TW (1982) The controversy over interspecific competition. Am Sci 70:586–590
Schoener TW (1983) Field experiments on interspecific competition. Am Nat 122:240–285
Schoener TW (1984) Size differences among sympatric, bird-eating hawks: a world-wide survey. In: Strong DR, Simberloff D, Abele LG, Thistle AB (eds). Ecological communities: conceptual issues and the evidence. Princeton University Press, Princeton, pp 254–281
Schoener TW (1985) Some comments on Connell's and my reviews of field experiments on interspecific competition. Am Nat 125:730–740
Sih A, Crowley P, McPeek M, Petranka J, Strohmeier K (1985) Predation, competition, and prey communities: a review of field experiments. Ann Rev Ecol Syst 16:269–311
Siivonen L (1974) Pohjolan nisäkkäät. Otava, Helsinki
Simmons R (1986) Ecological segregation of the Red-Breasted Sparrowhawk Accipiter rufiventris and six coexisting accipitrine raptors in Southern Africa. Ardea 74:137–149
Steenhof K, Kochert MN (1985) Dietary shifts of sympatric buteos during a prey decline. Oecologia (Berlin) 66:6–16
Storer RW (1966) Sexual dimorphism and food habits in three North American accipiters. Auk 83:423–436
Walter GH, Hulley PE, Craig AJFK (1984) Speciation, adaptation and interspecific competition. Oikos 43:246–248
Wiens JA (1983) Interspecific competition. Am Sci 71:234–235
Wiens JA, Rotenberry JT (1979) Diet niche relationships among North American grassland and shrubsteppe birds. Oecologia (Berlin) 42:253–292
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Korpimäki, E. Dietary shifts, niche relationships and reproductive output of coexisting Kestrels and Long-eared Owls. Oecologia 74, 277–285 (1987). https://doi.org/10.1007/BF00379371
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00379371