Enriching the isotopic toolbox for migratory connectivity analysis: a new approach for migratory species breeding in remote or unexplored areas

Abstract

Aim We examined three potential enhancements of the stable isotope technique for elucidating migratory connectivity in birds inhabiting poorly studied areas, illustrated for Eurasian cranes (Grus grus) that overwinter in and migrate through Israel. First, we examined the use of oxygen stable isotopes (d 18 O), seldom applied for this purpose. Second, we examined the relationship between ambient water d 18 O and hydrogen stable isotope (d 2 H) values derived from various models, to determine the geographical origins of migrants. Third, we introduced the use of probabilistic distribution modelling to refine the assignment to origin of migrants lacking detailed distribution maps.Location Feather samples were collected in the Hula Valley (northern Israel) and across the species breeding range in north Eurasia.Methods We analysed d 18 O and d 2 H in primary and secondary flight feathers using standard mass spectrometry. The maximum entropy (MAXENT) model was used to map the probability surface of potential breeding areas, as a Bayesian prior for assigning Hula Valley cranes to potential breeding grounds.Results We found that d 18 O was suitable and informative. The soil water isoscape performed better for d 18 O while precipitation isoscape was preferable for d 2 H. The MAXENT-based probability surface largely refined assignments. Overall, most (>85%) cranes were assigned to the area west of the Ural Mountains, but for two individuals, most of the assigned area (>90%) was farther east, suggesting, for the first time, that Eurasian cranes may undertake the North Asia-Middle East (and perhaps Africa) migration flyway.Main conclusions Our results call for broader use of d 18 O in migratory connectivity studies and for application of probabilistic distribution modelling. We also encourage investigation of factors determining d 18 O and d 2 H integration into animal tissues. The proposed framework may help improve our understanding of migratory connectivity of species inhabiting previously unexplored areas and thus contribute to the development of efficient conservation plans.

GPS-tracking reveals non-breeding locations and apparent molt migration of a Black-headed Grosbeak

“…Identifying and understanding patterns of connectivity between breeding and overwintering areas used by populations of Neotropical migrants is increasingly recognized as critical for informing full annual‐cycle conservation efforts (Webster and Marra , Pekarsky et al. ). For molt migrant species, identifying the stopover habitats where molting occurs may also be critical.…”

Predicting origins of passerines migrating through Canadian migration monitoring stations using stable-hydrogen isotope analyses of feathers: a new tool for bird conservation

“…However, both of these constraints can be improved and incorporated into assignment models using a more probabilistic-based approach as true priors in a Bayesian framework. For example, Pekarsky et al (2015) recently used probability of occurrence surfaces based on Maximum Entropy Modeling (MaxEnt version 3.3.3k; Phillips et al 2006) combined with stable-oxygen isotopes to infer origins of Common Cranes (Grus grus). Van Wilgenburg and Hobson (2011) also demonstrated how migration vectors derived from band recoveries can be applied as a Bayesian prior in isotopic assignments of birds and other wildlife (see also Hobson et al 2014).…”

Intrapopulation diversity in isotopic niche over landscapes: Spatial patterns inform conservation of bear–salmon systems

“…, Wunder , Pekarsky et al. ). Isotopic landscapes of dietary data can geographically characterize the diversity in realized dietary niche of specific prey contributions, and the corresponding ecological implications of predator–prey systems (Schindler and Lubetkin ).…”

“…When SIA data are tied to spatial and temporal information (e.g., island vs. mainland populations, discrete sampling locations), it is possible to characterize realized isotopic niche variation spatially within and among populations (e.g., Darimont et al 2009, Semmens et al 2009, Jaeger et al 2010, Ehrich et al 2015. Spatial representations of patterns from SIA, often denoted as isotopic landscapes or "isoscapes," have been used in migratory research to visualize geographic origins or movement and behavior patterns across landscapes (Hobson 2005, Hobson et al 2010, Wunder 2010, Pekarsky et al 2015. Isotopic landscapes of dietary data can geographically characterize the diversity in realized dietary niche of specific prey contributions, and the corresponding ecological implications of predatorprey systems (Schindler and Lubetkin 2004).…”