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Estimated probability of American Dipper occurrence by survey period. The first survey occurred in mid-June each year. Additional surveys followed every 2 weeks with the sixth survey conducted in early-to mid-September. Dashed lines on either side of the response curve represent 95% confidence intervals. Probability of occurrence is significantly lower when the response curve and the confidence intervals are completely below the average effect line.
Source publication
We studied summer use of high elevation lakes by American Dippers (Cinclus mexicanus) in the Trinity Alps Wilderness, California by conducting repeated point-count surveys at 16 study lakes coupled with a 5-year detailed survey of all available aquatic habitats in a single basin. We observed American Dippers during 36% of the point-count surveys an...
Context in source publication
Context 1
... over 4 years. They were observed in all 4 years at three lakes, 3 of 4 years at four lakes, 2 years at two lakes, and only 1 of the 4 survey years at one lake. Dippers were most often observed after the first survey in mid-June with no difference in the probability of occurrences during the rest of the surveys in July through mid-September (Fig. ...
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Citations
... Birds may shift upslope in the summer to exploit nesting opportunities (Boyle, 2008a;Green et al., 2015) or track pulses in arthropods and other food (Boyle, 2008b;Paxton et al., 2020;Supriya et al., 2019). The large temperature variation in temperate mountains may bring about patterns in elevational shifts similar to latitudinal migration, with montane species generally breeding at high elevations and spending the winter at lower elevations (Borras et al., 2010;Garwood et al., 2009;Ishtiaq & Barve, 2018). However, it is important to note that both latitudinal and elevational migration are not independent of each other and is often a matter of the degree to which a species may move along either axis. ...
Aim
Elevational migration is a globally ubiquitous animal behaviour. Understanding the mechanisms that drive variation in elevational movement can help explain the evolution of this widespread animal behaviour and its role in shaping montane life history. We examine the role of thermal regime (the intra‐annual variation in temperature experienced by a species), dispersal ability and diet in explaining the extent of elevational movements.
Location
Eastern and Western Himalayas.
Time Period
2011–2022.
Major Taxa Studied
Birds.
Methods
We used community science data from eBird to acquire checklist‐based observations of birds and used comprehensive data cleaning procedures and randomization tests to produce estimates of seasonal elevational shifts for 302 species of Himalayan birds. Using these data, we ran phylogenetic least squares regressions (PGLS) to test if the extent of elevational shift is driven by thermal regime, dispersal ability and diet.
Results
Most Himalayan birds (up to 65%) showed downslope shifts in the winter, although some (5%‐10%) low elevation species shifted upslope. Elevational shift was negatively associated with a species' thermal regime. Species that showed the greatest elevational shifts in both eastern and western Himalayas moved within the narrowest intra‐annual temperature regimes, but did not match their breeding range temperatures as closely as possible. Diet influenced elevational shift in both eastern and western Himalayas, while dispersal ability did not drive elevational shifts.
Main Conclusions
Species that show the biggest elevational shifts track thermal regimes most closely. However, in addition to tracking thermal regimes, diet and potentially habitat availability/preferences may drive seasonal elevational shifts. Our results show convergent evolution of elevational shifts across clades. Low elevation habitats are important not only for conserving low elevation birds but also for conserving wintering sites of most high elevation breeders.
... The drivers for uphill migration often differ from those of downhill migration, and they also differ among taxa because of differences in seasonal requirements. For ungulates and birds in temperate regions, uphill migration is often driven by the availability and quality of food resources and reduced predation risk at higher elevations during the spring and summer (Festa-Bianchet, 1988;Albon & Langvatn, 1992;Garwood et al., 2009), while downhill migration is often driven by cold temperature and precipitation, especially snow (O'Neill & Parker, 1978;Parrini et al., 2003). By contrast, several bat species in temperate regions migrate uphill during the autumn and winter because conditions at higher elevations are more suitable for hibernation and migrate downhill for breeding and rearing young (Esbérard et al., 2011;Voigt et al., 2014). ...
Animal migration has been the subject of intensive research for more than a century, but most research has focused on long‐distance rather than short‐distance migration. Altitudinal migration is a form of short‐distance migration in which individuals perform seasonal elevational movements. Despite its geographic and taxonomic ubiquity, there is relatively little information about the intrinsic and extrinsic factors that influence altitudinal migratory behaviour. Without this information, it is difficult to predict how rapid environmental changes will affect population viability of altitudinal migrants. To synthesize current knowledge, we compiled literature on altitudinal migration for all studied taxa, and identified the leading hypotheses explaining this behaviour. Studies of animal altitudinal migration cover many taxonomic lineages, with birds being the most commonly studied group. Altitudinal migration occurs in all continents except for Antarctica, but about a third of the literature focused on altitudinal migration in North America. Most research suggests that food and weather are the primary extrinsic drivers of altitudinal migration. In addition, substantial individual‐level variation in migratory propensity exists. Individual characteristics that are associated with sex, dominance rank, and body size explain much of the variation in migratory propensity in partially migratory populations, but individual‐level correlates are poorly known for most taxa. More research is needed to quantify the effects of habitat loss, habitat fragmentation, and climate change on altitudinal migrants. Demographic studies of individually marked populations would be particularly valuable for advancing knowledge of the cascading effects of environmental change on migratory propensity, movement patterns, and population viability. We conclude our review with recommendations for study designs and modelling approaches that could be used to narrow existing knowledge gaps, which currently hinder effective conservation of altitudinal migratory species.
... [1] [2-4] Cade and Hoffman 1993, Connelly 1988, Dixon and Gilbert 1964[5, 6] Dunning andBowers 1984, Horvath and[7-11] Garwood et al. 2009, Gillis et al. 2008, Grinnell and Miller 1944, Laymon 1989, Lorenz and Sullivan 2009[12, 13] Des Granges 1979, Solórzano et al. 2000[14-20] Boyle 2011, Chassot and Monge-Arias 2012, Chaves-Campos 2004, Chaves-Campos et al. 2003, Fraser et al. 2008, Loiselle and Blake 1991, Stiles 1980[21-27] Newsome et al. 2015, Tinoco et al. 2009, Strewe and Navarro 2003, Hobson et al. 2003, Hilty 1997, Hughes 1980, 1984[28] Beebe 1947;[29-31] Galetti 2001, Bencke and Kindel 1999, Areta and Bodrati 2010[28, 32-34] Beebe 1947, Bildstein 2004, Alves 2007, Capllonch 2007[35, 36] Borras et al. 2010, Klemp 2003[37, 38] Brambilla andRubolini 2009, De La Hera et al. 2014;[39] Burgess and Mlingwa 2000;[40, 41] Brown 2006, Johnson andMaclean 1994;[42] Lu et al. 2010;[43, 44] Kimura et al. 2001, Ryan 2012[45, 46] Dingle 2004[45, 46] Dingle , 2008[47] Nocedal 1994;[48] Stiles and Skutch 1989 high-elevation breeding areas (Powell and Bjork 2004). Satellite-tagged Nēnē exhibit considerable inter-individual flexibility in the duration and distance of migratory journeys, with some individuals making nonstop flights while others make multiple stopovers (Leopold and Hess 2014). ...
Altitudinal bird migration involves annual seasonal movements up and down elevational gradients. Despite the fact that species from montane avifaunas worldwide engage in altitudinal migration, the patterns, causes, and prevalence of these movements are poorly understood. This is particularly true in North America where the overwhelming majority of avian migration research has focused on obligate, long-distance, temperate–tropical movements. Elsewhere in the world, most altitudinal migrants are partial migrants, making downhill movements to nonbreeding areas. However, spatial and temporal patterns, the prevalence and predictability of migration at individual and population levels, and the ultimate ecological factors selecting for movement behavior vary considerably among taxa and regions. I conducted a systematic survey of the evidence for altitudinal migration to fill gaps in our understanding of this behavior among the landbirds of North America and Hawaii. Altitudinal migration was as prevalent as in other avifaunas, occurring in >20% of continental North American and nearly 30% of Hawaiian species. Of the species wintering within the USA and Canada, ∼30% engage in altitudinal migrations. Altitudinal migrants are far more common in the West, are taxonomically and ecologically diverse, and North American species exhibit patterns similar to altitudinal migrants elsewhere in the world. Because altitudinal migration systems are relatively tractable, they present excellent opportunities for testing hypotheses regarding migration generally. Altitudinal migration has likely been overlooked in North America due to contingency in the history of ornithological research. Our need to understand the patterns and causes of altitudinal migrations has never been greater due to emerging environmental threats to montane systems.
... 6 km (range 2-21 km) to breeding territories on creeks and streams at higher elevations. Migrants and their offspring leave these territories at the end of the breeding season [39], perhaps moving to even higher elevations [40], but are back on their wintering territories by the fall [36]. Residents in contrast occupy a multi-purpose territory year round. ...
Studies of partial migrants provide an opportunity to assess the cost and benefits of migration. Previous work has demonstrated that sedentary American dippers (residents) have higher annual productivity than altitudinal migrants that move to higher elevations to breed. Here we use a ten-year (30 period) mark-recapture dataset to evaluate whether migrants offset their lower productivity with higher survival during the migration-breeding period when they occupy different habitat, or early and late-winter periods when they coexist with residents. Mark-recapture models provide no evidence that apparent monthly survival of migrants is higher than that of residents at any time of the year. The best-supported model suggests that monthly survival is higher in the migration-breeding period than winter periods. Another well-supported model suggested that residency conferred a survival benefit, and annual apparent survival (calculated from model weighted monthly apparent survival estimates using the Delta method) of residents (0.511 ± 0.038SE) was slightly higher than that of migrants (0.487 ± 0.032). Winter survival of American dippers was influenced by environmental conditions; monthly apparent survival increased as maximum daily flow rates increased and declined as winter temperatures became colder. However, we found no evidence that environmental conditions altered differences in winter survival of residents and migrants. Since migratory American dippers have lower productivity and slightly lower survival than residents our data suggests that partial migration is likely an outcome of competition for limited nest sites at low elevations, with less competitive individuals being forced to migrate to higher elevations in order to breed.
