Search tactics of a pause-travel predator: adaptive adjustments of perching times and move distances by hawk owls (Surnia ulula)

SummaryAfter having erected artificial perches of different heights in a clear-cut, I studied the effect of perching height on the allocation of search and pursuit effort of 9 individuals of the hawk owl. Hawk owls are diurnal and locate their small mammal prey visually. Horizontal attack and move distances increased with perching height in most individual cases, as well as across cases. Prey detection and giving-up times increased with perching height in half of the individual cases, but not across cases. Attack and move distances increased with perching time in only a few individual cases, and not across cases. Perching height explained more of the variation in attack and move distances than did perching time. Move distance depended on both preceding and subsequent perching heights. When giving up a perch the owls on average moved slightly farther than the distance predicted if travel distance as well as overlap between successive search areas are to be minimized. When the ground was snow-free, distances of successful attacks tended to be shorter than those of unsuccessful attacks. Moreover, perches from which prey were captured, but not perches from which unsuccessful attacks were launched, tended to be lower than perches which were given up. This may suggest that the predator-prey distance is more critical to the probability of capture than to the probability of detection. Longer horizontal attack distances from higher perches suggest that the size of the area effectively searched around each perch increases with the height of the perch. Therefore, longer giving-up times on higher perches indicate allocation of more search time to larger search areas, and longer moves after giving up or before landing on higher perches indicate avoidance of overlap with the larger search areas of these perches. These adjustments of giving-up time and move distance allow hawk owls to forage efficiently.

[1]  Scott K. Robinson,et al.  Foraging Behavior of Forest Birds: The Relationships Among Search Tactics, Diet, and Habitat Structure , 1982 .

[2]  M. Andersson.  On optimal predator search , 1981 .

[3]  G. Sonerud.  What causes extended lows in microtine cycles? , 1988, Oecologia.

[4]  J. Fitzpatrick.  Search strategies of tyrant flycatchers , 1981, Animal Behaviour.

[5]  H. Henttonen,et al.  Gradients in density variations of small rodents: the importance of latitude and snow cover , 1985, Oecologia.

[6]  H. Southern,et al.  Owls of Europe , 1983 .

[7]  K. Norberg.  KeynoteAddress Evolution , Structure , and Ecology of Northern Forest Owls ' , 2022 .

[8]  T. Moermond.  The Influence of Habitat Structure On a Nolis Foraging Behavior , 1979 .

[9]  R. Eckhardt.  THE ADAPTIVE SYNDROMES OF TWO GUILDS OF INSECTIVOROUS BIRDS IN THE COLORADO ROCKY MOUNTAINS , 1979 .

[10]  J. Altmann,et al.  Observational study of behavior: sampling methods. , 1974, Behaviour.

[11]  S. G. Rudolph.  Foraging Strategies of American Kestrels During Breeding , 1982 .

[12]  T. Postelnicu,et al.  Sokal, R. R., and I. J. Rohlf: Biometry. W. H. Freeman and Company, San Francisco 1969, XXI + 776 S., 89 Abb., 56 Tab., Preis 126/— , 1970 .

[13]  J. Fitzpatrick,et al.  Foraging Behavior of Neotropical Tyrant Flycatchers , 1980 .

[14]  R. Green,et al.  Foraging behaviour of migrant pied flycatchers, Ficedula hypoleuca, on temporary territories. , 1980 .

[15]  T. G. Balgooyen.  Behavior and ecology of the American kestrel (Falco sparverius L.) in the Sierra Nevada of California , 1976 .

[16]  A. Tye.  FORAGING BEHAVIOUR AND SELECTION OF PREY AND PERCHES BY THE BUFFSTREAKED CHAT OENANTHE BIFASCIATA , 1988 .

[17]  E. Temeles.  Effect of prey consumption on foraging activity of Northern Harriers , 1989 .

[18]  S. Siegel,et al.  Nonparametric Statistics for the Behavioral Sciences , 2022, The SAGE Encyclopedia of Research Design.

[19]  M. Pienkowski,et al.  Changes in the foraging pattern of plovers in relation to environmental factors , 1983, Animal Behaviour.

[20]  Use of Perches as Vantage Points During Foraging By Male and Female Stonechats Saxicola Torquata , 1983 .

[21]  J. Moreno.  SEARCH STRATEGIES OF WHEATEARS (OENANTHE OENANTHE) AND STONECHATS (SAXICOLA TORQUATA): ADAPTIVE VARIATION IN PERCH HEIGHT, SEARCH TIME, SALLY DISTANCE AND INTER-PERCH MOVE , 1984 .

[22]  Prey detection in the red-backed shrike (Lanius collurio): an experimental study , 1985, Animal Behaviour.

[23]  N. Davies,et al.  Prey selection and the search strategy of the spotted flycatcher (Muscicapa striata): A field study on optimal foraging , 1977, Animal Behaviour.

[24]  B. Evans,et al.  Flexible search tactics and efficient foraging in saltatory searching animals , 1989, Oecologia.

[25]  G. Sonerud.  Effect of snow cover on seasonal changes in diet, habitat, and regional distribution of raptors that prey on small mammals in boreal zones of Fennoscandia , 1986 .