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H.2-1: GPS tracking data reveals daily spatio-temporal movement patterns of waterfowl

Presented by Michael L. Casazza - Email: mike_casazza@usgs.gov

Spatio-temporal movement patterns characterize relationships between organisms and their surroundings, and improve understanding of species ecology, activity budgets, bioenergetics, and habitat resource management. Highly mobile waterfowl, which can exploit resources over large areas, are excellent models to understand relationships between movements and resource usage, landscape interactions and habitat needs. We tracked 3 species of dabbling ducks with GPS in 201517 to examine fine-scale movement patterns over 24h periods (30min intervals), dividing movement pathways into temporally continuous segments and spatially contiguous patches. We quantified distances moved, area used and daily time allocation, using linear and generalized linear mixed models, investigating behavior through relationships between variables. Movements and space-use were small, and varied by species, sex and season. Gadwall (Mareca strepera) had shortest forage flights (FFDs): 0.50.7km, but longer within-area movements produced larger foraging patches. Pintails (Anas acuta) moved most, with FFDs 0.81.1km, were more likely to fly >300m, had more segments and patches per day which they revisited more frequently, and longest daily total movements. Sexes differed only during the post-hunt season when females moved more. 23.6% of segments were short duration (12 locations), 1/3 more than would be expected if random, and were more dispersed in the landscape than longer segments. 30min distances moved shortened as segment duration increased, likely reflecting phases of non-movement within segments. That ducks used smaller foraging and resting areas than expected or previously reported, implies foraging areas may be highly localized, and nutrients obtainable from smaller areas. Reduced movement over time demonstrates behavioral adjustments representing divergent energetic demands, the detection of which is a key advantage of higher frequency data. Ducks likely use less energy than currently predicted and management including distribution/configuration of essential habitat, may require reconsideration. Our study illustrates how fine-scale movement data can inform various fields of research.
Session: Movement & Tracking (Thursday, August 29, 13:20 to 15:00)