Movements and seasonal use of habitats by rural and urban female mottled ducks in southeast Florida

Abstract

Florida will continue to undergo high rates of habitat loss, primarily the result of urbanization. In addition, invasive species are a major threat to Florida's biodiversity. The Florida mottled duck (Anas fulvigula), a bird unique to the state, is particularly vulnerable to loss of wetland habitats and hybridization with feral mallards. Because mottled ducks are more likely to encounter feral mallards in urban habitats, we trapped and radiomarked adult females in urban (n = 99) and rural (n = 146) habitats to estimate home ranges and rates of movement into and out of urban areas. We also determined habitat use in urban and rural areas during the breeding (1 Feb–31 Jul), post‐breeding (1 Aug–18 Nov), and hunting (19 Nov–31 Jan) periods and estimated seasonal habitat selection of rural female mottled ducks. Urban females used mostly aquatic habitats in low and high intensity human development year‐round. Rural ducks used freshwater marshes throughout the year, but selection of other habitat types varied seasonally. Use of glades marsh and agricultural habitats by rural ducks peaked during the breeding season. Rural ducks selected artificial impoundments and reservoirs during the post‐breeding and hunting periods. Median home range size of rural females was more than 65 times greater than those of urban females. Our results suggest the spread of mallard genetic introgression caused by females leaving urban areas may be slow because as few as 6% of the adult females moved between urban and rural areas. Focusing wetland conservation efforts on freshwater marshes and artificial impoundments in south Florida would likely benefit mottled ducks. © 2014 The Wildlife Society.

Seasonal habitat selection and movements by mottled ducks

“…Estimates of home ranges and core areas for birds from our study were similar to estimates for birds in the Chenier Plain of Texas ( home range = 6,566 ha and core areas = 1,516 ha; Moon ). Our estimates for Georgia and South Carolina mottled ducks were greater than for birds using urban areas but less than for birds using rural areas in Florida (Varner et al ). We also found that mottled ducks avoided estuarine emergent wetlands during the molt season but selected for managed impoundments in all seasons; 72% of all locations recorded were in managed impoundments.…”

“…To evaluate seasonal movement and habitat selection of mottled ducks, we first adapted seasons from Varner et al () but adjusted them to reflect the hunting seasons in Georgia and South Carolina as follows: breeding (1 Feb–30 Jun), molt and post‐breeding (1 Jul–9 Sep), teal hunting season (10 Sep–19 Nov), and hunting season (20 Nov–31 Jan). We based teal and hunting seasons on the earliest opening date for those respective hunting seasons from 2013–2016.…”

“…In portions of its range in the WGC and Florida, mottled ducks are generally a resident species that use various habitats, including non‐tidal fresh to brackish marshes, flooded rice fields, and inland prairies of the WGC (Stutzenbaker , Zwank et al , Haukos et al , Moon ). Mottled ducks in Florida also use freshwater lakes and ponds associated with urban areas (Varner et al ) and freshwater emergent wetlands and wet prairies (Johnson et al , Bielefeld et al ). Previous research in South Carolina noted that water depth <25 cm (Weng ), and managed wetland impoundments and brackish wetlands (Shipes et al ) were important to mottled ducks.…”

“…For example, mean annual home ranges for females in Florida vary from 2,050–95,000 ha (Bielefeld et al ). Varner et al () reported that individuals living in urban areas had ranges of 232–598 ha, whereas individuals living in rural areas used ranges from 32,573–88,101 ha. In southeast Texas, breeding season home ranges of female mottled ducks varied from 650–4,200 ha (Rigby ) compared to coastal Texas where female breeding season home ranges varied 42.5–132 ha (Weeks ).…”

The movements of a recently urbanized wading bird reveal changes in season timing and length related to resource use

“…Human activities modify local abiotic conditions and resource availability, and since conditions experienced during one portion of the annual cycle may carry over into subsequent seasons, full annual cycle studies are needed to understand the fitness effects of behavioral changes relating to human modification of the landscape. Animals can exhibit either migratory and/or nomadic behaviors in response to variable resource availability; conversely, they can also become residents in a given area by changing their resource use, rather than location [3][4][5][6][7]. A more accurate measure of season initiation, or the change in seasonal state (e.g., non-breeding to breeding) is required to understand how populations are modifying their movements both temporally and spatially in response to altered land use.…”