Mallard Response to Experimental Walk‐In and Shooting Disturbance

Abstract

Spatial and temporal closures of anthropogenic activities are a common management strategy to increase waterfowl usage of an area. However, empirical evidence, specifically how individual waterfowl respond to disturbance, is lacking to support their efficacy. We exposed radiomarked mallards (Anas platyrhynchos) to walk-in, shooting, or no disturbance along the South Platte River corridor in Colorado, USA, from September to February during 2006-2007 and 2007-2008. Mallards exposed to shooting disturbance had greater mean flight distance after disturbance (FDAD) during September-November (4.58 km, 95% CI 5 3.55-5.62) than December-February (3.04 km, 95% CI 5 2.51-3.58) and were 35% and 17% greater than mean FDAD of mallards exposed to walk-in disturbance, respectively. Walk-in and shooting disturbance had a similar effect on return rates, and disturbed mallards had higher (0.09-0.41) movement probabilities away from and lower (0.15-0.20) probabilities of returning to treatment locations than controls. Probability of presence of disturbed mallards was 37% lower than controls during the daytime but was equal at night. Mallards exposed to walk-in (0.38 [95% CI 5 0.30-0.46]) and shooting (0.23 [95% CI 5 0.17-0.30] disturbance had low return rates the first afternoon after a disturbance compared to controls (0.71 [95% CI 5 0.65-0.77]). A high proportion of mallards exposed to walk-in (0.75 [95% CI 5 0.67-0.83]) and shooting (0.70 [95% CI 5 0.64-0.76]) disturbance returned to treatment locations in M 1 day. Managers may be able to more effectively manage disturbance regimes by 1) accounting for surrounding lands within ,10 km, especially lands within ,5 km, 2) being conscientious when establishing regulations that will affect levels of disturbance 1-2 days after a previous disturbance, and 3) considering shooting and walking disturbance equally for refuge design.

Mallard resource selection trade‐offs in a heterogeneous environment during autumn and winter

“…We detected that there was no longer a substantial influence of private marsh on selection after the FIRST half of the hunting season. We suggest this response was related to a shift in the balance of trade‐offs, because ducks continued to select for CWS‐NWA, a similar vegetation type, but with no mortality risk from hunting (Dooley, Sanders, & Doherty, , ; Madsen ). Disturbances and risks at private marshes may have had a chronic effect on Mallard distribution, making the cost associated with using this wetland type outweigh the benefit over time.…”

“…Based on the digital classification of resource types, private and public water had similar foraging resources but different mortality risks from hunting (Palumbo, ). Therefore, we suggest that ducks were selecting private water during the hunting season to benefit from reduced hunting pressure, relative to public water (Dooley, Sanders, & Doherty, ). Also, private marsh and CWS‐NWA (i.e., federally managed marsh) provided similar foraging benefits with different levels of mortality risk.…”

Factors Influencing a 24-Hour Time-Budget for Wintering Atlantic Brant

“…Natural and anthropogenic sources of diurnal disturbance also can reduce diurnal feeding opportunities and increase nocturnal activity (Owens 1977;Ydenberg et al 1984;Bélanger and Bédeard 1990;Ward et al 1994;Kahlert et al 1996;Riddington et al 1996). Additionally, hunting disturbance has the potential to shift geese feeding away from areas open to hunting during the day (Owens 1977;Stock 1993;Ward et al 1994), while using areas open and closed to hunting nocturnally (Burton and Hudson 1978;Cox and Afton 1997;Dooley et al 2010).…”

Full Issue

“…For most Nearctic ducks, this period extends nearly 8 mo and includes significant biological and social events (Weller 1988, Robertson and Cooke 1999, Baldassarre and Bolen 2006. Accessible, quality food and disturbance-free areas are essential resources for wintering waterfowl (Whyte and Bolen 1984, Legagneux et al 2009, Dooley et al 2010b). The survival of waterfowl in winter can be greatly affected by age, habitat conditions, body condition, hunting-related effects (e.g., disturbance, direct mortality), and the availability of sanctuary (Krementz et al 1988, Conroy et al 1989, Longcore et al 2000, Dooley et al 2010a, 2014.…”