Adam C. Behney
Tamarack State Wildlife Area
Estimate adult female, nest, and brood survival of northern bobwhites at Tamarack State Wildlife Area and evaluate effects of short-duration intensive grazing on these characteristics.
Assess nest and brood site selection of northern bobwhites in relation to grazing scheme.
Widespread suppression of historic disturbance regimes have reduced heterogeneity in vegetation communities on which many wildlife rely for various life events and stages. Northern bobwhites require areas of thicker grass cover for nesting within close proximity to more open areas with bare ground and abundant food producing forbs for brood rearing and feeding. Altered or eliminated vegetation disturbance has been implicated in the rangewide decline of northern bobwhite populations. Lack of disturbance on state wildlife areas in Northeast Colorado has caused the vegetation to become uniformly dense and tall which is likely not meeting the needs of all parts of the northern bobwhite life cycle. Some type of disturbance is required to reduce the vegetation biomass and create some of the open structure on which bobwhites rely. Grazing represents one of the only options for disturbance at Tamarack State Wildlife Area and other similar riparian areas in northeast Colorado. Whereas unmanaged continuous grazing has been linked to degradation of bobwhite habitat quality, short-duration intensive grazing holds promise to reduce the vegetation biomass and rejuvenate the habitat to become more attractive to bobwhites.
The objectives of this project are to assess the efficacy of using short-duration high-intensity grazing as a tool to improve northern bobwhite habitat. We will use a randomized block design in which we divide the study site into groups of four plots, one of which is grazed each year over a three year period and one is a control (Fig. 1). Beginning in late winter each year, we will capture bobwhites using walk-in traps and affix necklace-style VHF radio transmitters on 50 females. We will locate each radio-marked bobwhite three times per week and determine nest sites by observing birds in the same location on subsequent days. When nests hatch we will continue to monitor broods and on day 14 post-hatch we will flush the brood, and weekly thereafter to count chicks and assess brood status. To assess nest and brood site selection, we will sample vegetation at nest and brood sites and paired random points to represent available habitat. The overall goal is to estimate adult, nest, and brood survival as well as nest and brood site selection in relation to grazing treatment and other general habitat characteristics.
This study will directly inform management practices on Tamarack State Wildlife Area and potentially other riparian areas in northeastern Colorado and provide some baseline demographic information for use in future population modeling. The results will be applicable to managers wishing to manage vegetation in a way to provide the maximum benefit to northern bobwhites.