Facultative Migration Research Articles

Seasonal migrations of black bears (Ursus americanus): causes and consequences

American black bears frequently abandon their home ranges in late summer and move to feeding areas to fatten themselves for hibernation. We examined seasonal movements of 206 radio-collared bears in north-central Minnesota during 1981–1990. We exploited the variability in this long-term data set to test tradeoffs for animals leaving their home range. Late summer movements were common for both sexes and all ages (39% of females, 44% of males), but were variable from year-to-year in prevalence, timing, and destination. Bears typically left their summer home ranges in August and returned ~6 weeks later in September or October. Most traveled southward, where acorns were more plentiful (median = 10 km for females, 26 km for males; maximum = 168 km). These facultative migrations were most common when rich resources were available outside home ranges. Bears were least apt to leave when foods were scarce in their home range, possibly sensing a risk of migrating during a widespread food failure. Among females, those whose body mass was close to a reproductive threshold were most prone to migrate. Migrating bears were less likely to be killed by hunters, suggesting that they were especially vigilant.

Balancing Aquatic Habitat Fragmentation and Control of Invasive Species: Enhancing Selective Fish Passage at Sea Lamprey Control Barriers

AbstractBarriers to prevent spawning migrations of sea lampreys Petromyzon marinus remain an important component of an integrated sea lamprey management program in the Laurentian Great Lakes. Concerns about effects on nontarget fishes have led to the construction of specially designed vertical‐slot trap‐and‐sort fishways to mitigate potential barrier effects. To improve passage at these fishways, we used passive integrated transponder technology to assess the performance of two fishways located on low‐head sea lamprey barriers. Fishways on the Big Carp River (which flows into Lake Superior) and Cobourg Brook (which flows into Lake Ontario) were assessed for attraction efficiency, trap attraction and retention, and passage efficiency. Based on the results of these assessments, fishways were modified by increasing the trap volume and altering the funnel characteristics to reduce escapement from the trap and then reassessed. Attraction efficiency for all tagged fish was high (≥80%) at both sites in all years. Fishway modifications improved passage from 35% in 2003 to 88% and 64% in 2004 and 2005, respectively, at the Big Carp River. As expected, white suckers Catostomus commersonii, an obligate migrant, had higher attraction and passage efficiency, fewer passage attempts, and shorter migration delay than did rock bass Ambloplites rupestris, a facultative migrant. No improvements were seen at Cobourg Brook, where passage efficiency remained low (7% in 2003, 10% in 2005), probably because of the loss of attraction flow. At both fishways, individual fish averaged 3‐10 attempts to pass through the fishways and had their migrations delayed 1‐2 weeks. The observed improvements to the Big Carp River fishway, which resulted in high fishway attraction and passage rates for white suckers, suggest that vertical‐slot fishways can help mitigate the effects of low‐head barriers for some species. Our study provides a rigorous quantifiable approach to assessing fishway performance that can be employed widely and successfully to assess initial fishway design and subsequent modifications.

EVIDENCE FOR SEASONAL MOVEMENTS BY ROCK KESTRELSFALCO TINNUNCULUSAND LANNER FALCONSF. BIARMICUSIN SOUTH AFRICA

Summary Van Zyl, A.J, Jenkins, A.R. & Allan, D.G. 1994. Evidence for seasonal movements by Rock Kestrels Falco tinnunculus and Lanner Falcons F. biarmicus in South Africa. Ostrich 65:111-121. Patterns of seasonal movement by Rock Kestrels Falco tinnunculus and Lanner Falcons F. biarmicus in South Africa were determined using data from the Southern African Bird Atlas Project, road transect counts, ringing recoveries and other sources. Both species were found to be partial, facultative migrants, and Lanner Falcon movements involved mostly immature birds. Rock Kestrels were found to concentrate in the southwest of the country in the breeding season, and to move north and east in the non-breeding season. Lanner Falcons concentrated in the east of the country during the breeding season, and moved into the west in the non-breeding season. The movement by both species into the arid northwest of the country is probably associated with dramatic increases in prey abundance, in turn associated with summer rah events...

Carrying Capacity of Staging Areas and Facultative Migration Extension in Common Cranes

This is a contribution to projects PB87-0389 and PB91-0081 of the Direccion General de Investigacion Cientifica y Tecnica.

Migration and the effect of three environmental factors on the pre‐reproductive period of the cotton‐boliworm moth, Helicoverpa armigera

ABSTRACT. Migration by noctuid moths generally occurs while the adults are sexually immature, and so the pre‐reproductive period provides an indication of the time available for migratory flight. Helicoverpa armigera (Hb.) (Lepidoptera: Noctuidae) is considered to be a facultative migrant, emigrating in response to a deterioration in local environmental conditions for adult survival and larval development; hence the effects of temperature, vapour‐pressure deficit and the availability of sugar solution on the duration of the pre‐reproductive period are investigated. Temperatures below 28oC lengthened female pre‐reproductive periods but, contrary to the findings of Isley (1935) for Helicoverpa zea (Boddie), temperatures above 28oC shortened them. Females maintained at a vapour‐pressure deficit of 23.7 ± 0.5 mmHg (c. 12% r.h.) and 6.45 ±0.15mmHg (c. 76% r.h.) did not have significantly different pre‐reproductive period distributions. The availability of 10% w/v sugar solution (provided ad libitum) had a marked effect on both the survival and the pre‐reproductive period of both sexes. Moths given water for four nights followed by sugar solution thereafter, took significantly longer to reach reproductive maturity than those given sugar solution from emergence. Survival to reproductive maturity of moths given water only throughout their lives was poor (c. 20%). The significance of these findings to the migratory behaviour of H. armigera is discussed.

Evolutionary aspects of orientation and migration in birds

Evolutionary aspects of avian migratory orientation and navigation are reviewed. A theoretical approach to the evolution of complex (endogenously programmed) migratory behavior is presented using the comparative method of ordering a progression in existing behavioral characteristics from dispersal, to facultative migration, to obligate migration.

Facultative Migration in Yellow-Eyed Juncos

Journal Article Facultative Migration in Yellow-Eyed Juncos Get access Eric G. Horvath, Eric G. Horvath 1310 Cleveland, Corvallis, OR 97330 Search for other works by this author on: Oxford Academic Google Scholar Kimberly A. Sullivan Kimberly A. Sullivan Department of Biological Sciences, State University of New York, Albany, NY 12222 Search for other works by this author on: Oxford Academic Google Scholar The Condor, Volume 90, Issue 2, 1 May 1988, Pages 482–484, https://doi.org/10.2307/1368577 Published: 01 May 1988 Article history Received: 10 June 1987 Accepted: 27 October 1987 Published: 01 May 1988

Additional Evidence of Nocturnal Migration by Yellow-Rumped Warblers in Winter

Migration is a response to changing environmental conditions (Gauthreaux 1982). Migratory behavior spans a continuum from highly fixed behavior (obligate migration) to very flexible behavior (facultative migration). Whereas facultative migration occurs in response to deteriorating environmental conditions, obligate migration appears to be fundamentally a result of an endogenous, circannual program (see Gwinner 1986 for a recent review). Even obligate migrations, however, are not performed entirely without integration of environmental information. For example, migrants make daily decisions to migrate or not to migrate based upon environmental factors such as weather conditions, food and water availability at stopover sites, and competition (e.g., Rappole and Warner 1976, Richardson 1978, Mehlum 1983, Biebach 1985, Gwinner 1986, Biebach et al. 1986). The degree to which migratory behavior is subject to environmental influence appears to be quite variable (Terrill and Ohmart 1984). There is evidence that at least some species of annual, migrant passerines facultatively extend migration after the fall migratory period if environmental conditions become unfavorable for overwinter survival at a particular locality (Perdeck 1964, Niles et al. 1969, Moreau 1972, Lack 1983; Terrill and Ohmart 1984; Terrill 1987, in press). Presumably, the ability to perform facultative migrations enables these birds to respond to relatively unpredictable winter environments by migrating in an appropriate direction if conditions necessitate it. Patterns of migration and distribution of Yellowrumped Warblers (Dendroica coronata) indicate that they switch from an obligate phase to a facultative phase over the course of fall migration (Terrill and Ohmart 1984). Winter populations shift southward if conditions become unusually severe. When placed in Emlen funnels (Emlen and Emlen 1966), Yellowrumped Warblers showed southerly nocturnal orientation into early January (after which no birds were tested). While the orientation data support the hypothesis that winter movements like fall movements are nocturnal, the evidence is indirect. Here we present direct evidence that winter movements by Yellow-rumped Warblers are in fact noctur' Received 15 April 1987. Final acceptance 27 August 1987. 2 Present address: 208 Junius St., Thomasville, GA 31792. SHORT COMMUNICATIONS 261

Facultative Extension of Fall Migration by Yellow-Rumped Warblers (Dendroica coronata)

Abstract Many nocturnally migrating birds show at least some degree of winter site fidelity. Laboratory tests of nocturnal activity, or Zugunruhe patterns, and displacement experiments indicate that migratory distances may be under endogenous control. Yellow-rumped Warblers (Dendroica coronata auduboni) displayed a southerly nocturnal orientation well into winter months, past the conventional migratory period. Additionally, population shifts between highly isolated, limited, desert riparian habitats reflected a facultative migration from north to south. The magnitude of movement was correlated with food-resource abundance, which was dependent on climatic conditions. This suggests that the birds maintain a physiological state that enables them to winter as far north as possible but allows for a correctly oriented movement if conditions become unfavorable. Our results indicate considerable plasticity in what is generally considered a more rigidly fixed process.

Experimental studies of migration in bugs of the genus Dysdercus.

Using a tethered flight technique, migration was studied in the African cotton stainer bugs Dysdercus fasciatus Sign., D. nigrofasciatus Stål, and D. superstitiosus (F.) (Heteroptera: Pyrrhocoridae). The flight system of males of all three species matures in 4-6 days post-eclosion, and flight can continue throughout life. Fed females of D. fasciatus do not fly, but rather histolyse the flight muscles and develop oocytes. Fed females of D. nigrofasciatus and D. superstitiosus exhibit some flight at 4 days post-eclosion, but flight is essentially absent at 6 days when flight muscle histolysis and oögenesis are in progress. Starved females of all three species undertake considerable flight and do not histolyse the flight muscles or develop oöcytes. In starved pairs coupling frequency is lowered permitting increased migration. The three species are thus facultative migrants using starvation as a releasing cue. D. fasciatus feeds on baobab (Adansonia) fruits which are seasonally abundant and is the most opportunistic species with the highest reproductive potential and no flight in the presence of food. D. nigrofasciatus feeds on a variety of herbaceous annuals and perennials; it follows an intermediate migration and reproductive strategy. Finally D. superstitiosus is the most catholic in its food habits and has the lowest reproductive potential. Both of the latter species retain some flight capacity even when fed, presumably so that individuals can locate suitable host plants.