Behavior of Stiff-Tailed Diving Ducks and West Indian Whistling Ducks in Laguna Cartagena National Wildlife Refuge, Puerto Rico

Masked ducks (Nomonyx dominicus), migratory northern ruddy ducks (Oxyura jamaicensis jamaicensis), non-migratory West Indian ruddy ducks (Oxyura j. jamaicensis Gmelin), and West Indian whistling-ducks (Dendrocygna arborea) are all duck taxa that have declining populations in Puerto Rico. Masked ducks are listed as endangered in Puerto Rico and are a species of concern in the Caribbean while West Indian whistling ducks are considered an at-risk species listed as vulnerable. All 4 taxa of duck have areas of their life history where information is lacking including behavioral information. I studied the 4 taxa of duck at Laguna Cartagena National Wildlife Refuge from January--April 2015 and 2016. I quantified diurnal and nocturnal time activity-budgets of masked ducks (n = 142), West Indian ruddy ducks ( n = 3,765), and Northern ruddy ducks (n = 1,401) and also collected dive and inter-dive times on masked ducks (n = 60), West Indian ruddy ducks (n = 445), and northern ruddy ducks (n = 70). Behaviors varied among taxa, between sexes, and between diurnal and nocturnal sampling periods (P \u3c 0.01). Resting and sleeping were common behaviors observed during the day and night, but all three taxa fed more at night with more time spent feeding by West Indian ruddy ducks (Day, x¯ = 12.3% SE = 0.85, Night, x¯ = 19.8% SE = 0.68) than the northern ruddy ducks (Day, x¯ = 4.4% SE = 0.75, Night, x¯ = 6.3% SE = 1.9), but northern ruddy ducks were observed to have a longer dive time (22.9+0.75 seconds) than West Indian ruddy ducks (18.8+0.02 seconds). Northern ruddy ducks and West Indian ruddy ducks time-activity budgets varied with 7 of 8 behavioral categories during the day and 5 of 8 behavioral categories at night differing. Ecological differences such as body size or migration of northern ruddy ducks may account for the differences in behavior when compared to non-migratory West Indian ruddy ducks.;I calculated average flock size and total numbers, and provide updated numbers on West Indian whistling ducks in Puerto Rico. Previous estimates of West Indian whistling ducks in Puerto Rico were about 100 individuals, but when I conducted ten 8-hour night observations at Laguna Cartagena National Wildlife Refuge between 19 January 2016 and 8 April 2016, I found an average of 131.9 (SE=4.5) with a high count of 153 individuals. The West Indian whistling ducks used the lagoon at night arriving from the West 2--67 minutes after sunset with an average flock size of 4.65 (SE=0.6). They departed to the West before sunrise and are likely roosting during the day in the mangroves of Refugio de Aves de Boqueron. My counts indicate that the population of West Indian Whistling-Ducks in Puerto Rico is larger than previously estimated. To keep the ducks year round, it is suggested not to drain the entire lagoon at the same time so they have a place to feed