hunting20 spun

Waterfowl managers rely upon estimates of survival to aid in assessing waterfowl population statusand to guide management decision-making (Nichols et al. 1995, Johnson et al. 1997). Overwinteringsurvival (i.e. winter and autumn) is essential to managers because hunter harvest during regulatedhunting seasons occurs during this time (Anderson 1975, Nichols et al. 2007) and hunter survivaland harvest may be influenced by hunting regulations (Smith & Reynolds 1992, Menu et al. 2002,Otis 2004, Usa Fish and Wildlife Service 2008). One regulation type open to United states states aresplit hunting seasons, the location where the hunting season is separated into two or more segments(Ladd et al. 1989). The U.S. Fish and Wildlife Service first offered the split-season solution to all U.S.states in 1948 (Ladd et al. 1989), and by the mid-1980s, approximately one half of the states withinthe U.S. adopted split hunting seasons (Baldassarre & Bolen 2006). The intention of split huntingseasons is to increase hunter opportunity and success by better allocating hunting days to fitwaterfowl migrations using an area and by restoring waterfowl naivety to hunting pressure duringnon-hunting periods (Baldassarre & Bolen 2006). The efficacy of split hunting seasons has only beeninvestigated a bit and the relationship of overwintering waterfowl survival to periods of time withinthe hunting months are unknown, however.

Previous studies have found hunting to get the principle cause of waterfowl mortality during theoverwintering season (Migoya & Baldassarre 1995, Cox et al. 1998, Fleskes et al. 2002, Fleskes etal. 2007), minimizing survival continues to be documented during hunting periods in comparisonwith non-hunting periods (Cox et al. 1998, Fleskes et al. 2002, Moon & Haukos 2006). Additionally,Fleskes et al. (2007) found an inverse relationship between overwintering survival of femalemallards Anas platyrhynchos in centralCalifornia and USA, and the amount of hunting days. Huntingdecreases survival directly through hunter harvest and crippling, and indirectly throughdisturbance, which increases energy usage and causes waterfowl to prevent more preferred feedingand roosting areas (Fox & Madsen 1997). Pertaining to waterfowl survival within hunting periods,waterfowl mortality has been documented as being higher on the onset of hunting periods (Longcoreet al. 2000, Davis 2007, Fleskes et al. 2007), likely as a result of waterfowl naivety to huntingpressure and increased hunter participation. Other studies, however, have discovered mortality fromhunting being below, or just like, other causes of mortality (Bergan & Smith 1993, Bielefeld & Cox2006, Moon & Haukos 2006) and get observed similar (Miller et al. 1995, Lee et al. 2007) or lower(Davis 2007) survival during non-hunting periods, than during hunting periods.

Overwintering waterfowl survival is additionally affected by environmental factors and the bodycondition. Higher overwintering survival is documented during years of increased precipitation andhabitat conditions (Migoya & Baldassarre 1995, Moon & Haukos 2006, Fleskes et al. 2007). Bergan& Smith (1993) found that survival of female mallards inside the Playa Lakes Region ofnorthwesternUSA and Texas, decreased following severe weather conditions (i.e. five events of[degrees]C with snow cover) as did Jeske (1991) for female mallards inside the San Luis Valley ofColorado, USA, particularly after snow accumulation which reduced food availability. Patterns areless general, whilst the relationship between body condition and overwintering survival has receivedmuch attention. Some studies have supported the hypothesis that better body condition increasesoverwintering decreases and survival susceptibility to harvest (Hepp et al. 1986, Dufour et al. 1993,Heitmeyer et al. 1993, Robb 2002), while other research has not found this relationship (Jeske et al.1994, Cox et al. 1998, Lee et al. 2007). Individuals in poor body condition maybe more likely to beunpaired and consequently more quickly interested in decoys, more prone to disease, compelled touse habitats with greater hunting pressure and less centered on hunter and predator avoidance dueto spending more http://www.snipercentral.com/ hours searching for food (Hepp et al. 1986, Fleskeset al. 2002). Body condition of mallards has been shown to decrease during cold temperaturesevents (Whyte & Bolen 1984, Robb et al. 2001). Colorado mallards might be more vulnerable tomortality after severe weather as a result of low endogenous energy stores (Jeske 1991, Dugger etal. 1994).

Uncertainty are available for the standards affecting overwintering waterfowl survival, without anystudy, to your knowledge, has empirically tested for effects linked to the opening of hunting periods.Given this uncertainty and the widespread use of split hunting seasons in the USA, we estimatedadult mallard daily survival rates down the South Platte River corridor in northeastern Coloradoduring September--February. We tested a priori hypotheses about differences in survivalbetweensexes and years, different non-hunting and hunting efforts and periods intervals withinhunting periods (i.e. beginning 1-3 weeks of hunting periods, weekends and holiday weeks), anddetermined the impact of body condition and environmental conditions (i.e. daily minimumtemperature and accumulated snowfall) on overwintering survival. In relation to our findings, our

company offers recommendations which might be employed by managers to affect overwinteringsurvival.

Material and methods

Study area

We conducted our study about the South Platte River corridor (i.e. [approximately comparable to] 10km buffer surrounding the South sniper scope Platte River) in Sedgwick, Washington, Morgan andLogan counties in northeastern Colorado. Most wetlands and bodies of water in these counties are inthe South Platte River corridor. During 2005/06, the pilot study year, our study area included theSouth Platte River corridor from Fort Morgan east for the Colorado-Nebraska state line,approximately 150 contiguous kilometres. During 2006/07 and 2007/08, two smaller study areasinside the 2005/06 study area were utilized. The eastern study area extended in the town ofSedgwick west towards the town of Iliff, approximately 56 km. The western study area extendedfrom the city of Sterling west to Snyder, approximately 48 km. Natural vegetation is shortgrassprairie, dominantly grama species Bouteloua spp. and buffalograss Buchloe dactyloides withcottonwoods Populus spp. occurring along wetlands (Ringelman et al. 1989). Primary utilisation ofthe landscape is cattle production and farming, primarily corn.

Trapping and tracking

We radio-marked 235 adult (after-hatch year) mallards in the overwintering seasons of 2005/06

(pilot year), 2006/07 and 2007/08: 14 females and 24 males in 2005/06, 35 females and 60 males in2006/07 and 54 females and 48 males in 2007/08. Mallards were trapped with baited swim-in orwalk-in funnel traps during September-January, except that trapping began in late November duringthe 2005/06 season. We measured body mass (g) and wing length (mm) upon capture, except during2005/06 (N = 38), to calculate body condition index (BCI = body weight/wing length; Ringelman &Szymczak 1985). We used backpack VHF radio-tags, which weighed approximately 25 g (modelA1820 manufactured by Advanced Telemetry Systems (ATS)). Battery was approximately ninemonths. Radio-marked mallards were located with vehicle mounted Yagi antennas. Overwinteringsurvival was monitored from 1 December-21 February during 2005/06, 15 September-10 Februaryduring 2006/07 and 9 September-13 February during 2007/08.

During 2005/06, radio-marked mallards were found on average three times daily (range: 1-15) for 3-7 consecutive days separated by 1-15 times of no monitoring. During 2006/2007 and 07/08, radio-marked mallards were located 2-3 times daily for about fourteen days separated by 3-19 times of nomonitoring. Radio-tags sending a mortality signal (i.e. signal doubled in frequency after four hours ofinactivity) were recovered as quickly as possible to find out source of death. Carcasses, whenavailable, were inspected for signs and symptoms of predation and hunter crippling (i.e. shotgunpellet wounds and shattered bones). We recorded mallards found dead from apparent crippling andothers reported harvested by hunters as hunting mortalities. Other mortalities were recorded asnon-hunting mortalities (often known as natural mortalities; see Bergan & Smith 1993, Moon &Haukos 2006, Davis 2007).

Statistical analysis

We used the nest survival model (Dinsmore et al. 2002, Rotella et al. 2004) in Program MARK (White& Burnham 1999) to estimate daily survival rates. The nest survival model can be extended for someother known-fate data such as radio-telemetry data, when marked animals will not be monitored atregular intervals of your time (Schwartz et al. 2006, Mong & Sandercock 2007), as were our data.We excluded all data from the first four days after radio-tag attachment to protect yourself fromemigration and mortality biases associated with capture, radio and handling-tag effects (Cox & Afton

1998). Radio-marked mallards without detectable signal within our study area or the ones that wererecovered dead outside our study area were censored through the survival analysis with the lasttime these folks were located alive within our study area.

Based on previous research, preliminary modeling and also to keep the dimensions of our model setmanageable, we included sex as well as a parameter designating hunting periods from non-huntingperiods in all models. We considered other variables to evaluate variation in mallard survival relativeto year (2005/06, 2006/07 and 2007/08), different hunting periods (H), different non-hunting periods(NH), time intervals within hunting periods (opening effect for just one, several weeks (1 WK, 2 WKand three WK), holiday effect (HOL), quadratic trend across time (T2), body condition index (BCI)and environmental factors (accumulated snowfall (SNOW) and daily minimum temperature (TEMP);see Table 1 for descriptions). Temperature and precipitation data were taken from the Akron 4 E,Colorado weather station (National Climatic Data Center 2008), the elements station nearest ourstudy area.