Gyps species declined rapidly between the late 1990s and early 2000s in southern Asia due to the use of diclofenac and are listed as Critically Endangered species. Long-term data on breeding ecology is essential to understand the population trends of these threatened species. This study assessed the breeding phenology and reproductive performance of two critically endangered Gyps species—Long-billed Gyps indicus (Scopoli) (LBV) and White-rumped Gyps bengalensis (Gmelin) (WRV) vultures—through long-term monitoring at breeding colonies in Kaghaznagar and Sironcha Forest Divisions in the Deccan Plateau of India between 2010 and 2021. LBV began their nest construction and copulation in the second week of October, and ended in the fourth week of November, while the WRV completed the same between the first and second weeks of October. LBV started egg-laying during the first week of December and ended in the first week of January, with a peak during the third week on 14 December, and the mean incubation period was 54±1 days. The WRV completed their egg-laying early, during the second and third weeks of October, and peaked during the second week on 14 October and had a relatively longer incubation of 61±1 days. For LBV, hatching peaked during the first week of February, and the mean nestling period was 103±2 days, while for WRV hatching peaked much earlier, during the third week of December and the mean nestling period was 105±1 days. Overall nest success, breeding success, and productivity estimated based on 159 breeding pairs of LBV observed over 12 years were lower compared to that of 124 breeding pairs of WRV observed over 6-year period. The decline in breeding success of LBV since 2019 is discussed in light of cattle poisoning reported in 2018, and the reopening of the Sirpur paper industry (Kaghaznagar) in 2017 that discharges its hazardous effluent into the Peddavagu stream. Therefore, the present study suggests long-term monitoring of breeding colonies including evaluation of the drivers of population and breeding, molecular and toxicological studies, and implementation of Vulture Safe Zones to save these critically endangered Gyps vultures from local extinction.
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