Partial Altitudinal Migration of a Himalayan Forest Pheasant

Abstract

BackgroundAltitudinal migration systems are poorly understood. Recent advances in animal telemetry which enables tracking of migrants across their annual cycles will help illustrate unknown migration patterns and test existing hypotheses. Using telemetry, we show the existence of a complex partial altitudinal migration system in the Himalayas and discuss our findings to help better understand partial and altitudinal migration.Methodology/Principal FindingsWe used GPS/accelerometer tags to monitor the migration of Satyr tragopan (Tragopan satyra) in the Bhutan Himalayas. We tagged 38 birds from 2009 – 2011 and found that tragopans are partially migratory. Fall migration lasted from the 3rd week of September till the 3rd week of November with migrants traveling distances ranging from 1.25 km to 13.5 km over 1 to 32 days. Snowfall did not influence the onset of migration. Return migration started by the 1st week of March and lasted until the 1st week of April. Individuals returned within 4 to 10 days and displayed site fidelity. One bird switched from being a migrant to a non-migrant. Tragopans displayed three main migration patterns: 1) crossing multiple mountains; 2) descending/ascending longitudinally; 3) moving higher up in winter and lower down in summer. More females migrated than males; but, within males, body size was not a factor for predicting migrants.Conclusions/SignificanceOur observations of migrants traversing over multiple mountain ridges and even of others climbing to higher elevations is novel. We support the need for existing hypotheses to consider how best to explain inter- as well as intra-sexual differences. Most importantly, having shown that the patterns of an altitudinal migration system are complex and not a simple up and down slope movement, we hope our findings will influence the way altitudinal migrations are perceived and thereby contribute to a better understanding of how species may respond to climate change.

Altitudinal migration by birds: a review of the literature and a comprehensive list of species

“…However, recent technological advancements such as GPS/accelerometer tags (Norbu et al. ) and miniature video‐loggers (Rutz and Troscianko ) may make it easier for investigators to monitor bird movements. Analysis of stable isotopes also holds promise for the study of bird altitudinal migration (Webster et al.…”

“…,b, Norbu et al. ). In the tropics, altitudinal migration appears to be especially common (Blake and Loiselle , Loiselle and Blake , Hobson et al.…”

Altitudinal migration: ecological drivers, knowledge gaps, and conservation implications

“…For example, female satyr tragopan in the Himalayas are more likely to migrate from higher‐elevation summer to lower‐elevation winter grounds compared to males, consistent with prediction of the arrival‐time hypothesis. However, there was no difference in the distances travelled between male and female migrants which is inconsistent with the prediction that females travel further during migration because they do not need to stay close to breeding territories (Norbu et al ., ). Further, the arrival‐time hypothesis predicts that, by remaining close to the breeding ground, males are more likely to secure higher quality breeding territories and achieve higher reproductive success.…”

“…Although widespread both geographically and taxonomically, studies of the patterns and causes of altitudinal migration are relatively uncommon. Numerous studies have examined movement patterns and migration routes of long-distance migrants (Hughes et al, 1998;Fox, Glahder & Walsh, 2003;Luschi, Hays & Papi, 2003;Thirgood et al, 2004;Block et al, 2005;Stutchbury et al, 2009;Horton et al, 2011;Alves et al, 2013;Trierweiler et al, 2014), but similar studies on altitudinal migrants are much more limited (but see Powell & Bjork, 2004Poole & Mowat, 2005;Sawyer et al, 2009;Blake et al, 2013;Norbu et al, 2013;Leopold & Hess, 2014). The trade-offs made by altitudinal migrants are similar to those facing long-distance migrants, although the costs may be lower because altitudinal migrants cover much shorter distances (Dingle & Drake, 2007).…”

Seasonal patterns in δ2H values of multiple tissues from Andean birds provide insights into elevational migration

“…Radio‐transmitters (e.g., Leopold and Hess ) and GPS locators or geologgers (e.g., Norbu et al. ) have also been used to track elevational migrants but weight or cost, respectively, may limit their use. Hydrogen isotope (δ 2 H) analysis has become a powerful alternative technique for studying bird movement across both latitudes and elevations (Rubenstein and Hobson ).…”