Unravelling the major gap for Hooded Grebe conservation: migration and movements

The critically endangered Hooded Grebe (Podiceps gallardoi) breeds in plateaus of western Santa Cruz, Argentina. It overwinters in estuaries at the Atlantic coast, in Santa Cruz. Its migratory behavior and movements are unknown. A survey of 400 lakes at 7 plateaus from 2009 to date showed that numbers across seasons in each plateau did not change (x2<0.001). Tissue samples of 51 individuals from two plateaus (Buenos Aires –BALP– n=31; Siberia n=20) were analyzed for testing breeding site fidelity. We sequenced mtDNA (control region, 353 bp), and analyzed population structure with AMOVA. Genetic variability between them explained 11% of the variation, and haplotype frequency distribution was significantly different between plateaus (FST=0.1,p=0.009). Since 2011 we tagged 53 individuals at BALP and Strobel plateaus. Two juveniles and adults banded at BALP were detected nesting at the same plateau. An adult and a juvenile banded at BALP were detected at the Río Gallegos estuary (April). Lastly, we monitored the three main estuaries since 2011 and found a temporal trend, with early presence (April-May) in southern estuaries and a later northward displacement (June-August). The results suggest a phylopatric behavior, and number variations among lakes suggest fidelity at the scale of plateau, instead of specific lakes. The northwest – southeast migratory routes are likely to differ between autumn and spring migration. The information obtained is essential to understand population dynamic of Hooded grebes and the importance of each plateau as reproductive habitat and the role of each estuary during different stages of its migratory cycle.