North-south gradient in survival rates in midcontinental populations of mallards

Journal of Wildlife Management



I used band recovery data to test for the existence of a north-south gradient in survival and recovery rates for midcontinental populations of mallards (Anas platyrhynchos) during 3 time periods (1962-70, 1971-78, 1979-84). Mean annual survival rates for adult males and females were significantly associated with mean banding latitude (P < 0.0001 and P < 0.0004, respectively) and time period (P < 0.0001 and P < 0.001, respectively). Survival rates for both adult males and females were higher in the north and lower in the south. Because individuals from the northern regions migrate farther, the cost of migration in terms of survival was lower than some other factor(s) that may cause the gradient. The relationship between mean banding latitude and mean annual recovery rates was marginally significant for adult males (P = 0.043) but not for adult females (P = 0.183), suggesting that the gradient was not due to differential harvest pressure. At present, the north-south gradient in survival rates cannot be explained but may be caused by similar north-south clines in predation, habitat degradation, land use, and/or agricultural practices.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title North-south gradient in survival rates in midcontinental populations of mallards
Series title Journal of Wildlife Management
Volume 54
Issue 2
Year Published 1990
Language English
Contributing office(s) Patuxent Wildlife Research Center
Description 206-210
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Journal of Wildlife Management
First page 206
Last page 210