hunting20 spun

Waterfowl managers depend on estimates of survival to assist in assessing waterfowl populationstatus as well as to guide management decision-making (Nichols et al. 1995, Johnson et al. 1997).Overwintering survival (i.e. winter and autumn) is essential to managers because hunter harvestduring regulated hunting seasons occurs during this period (Anderson 1975, Nichols et al. 2007) andhunter survival and harvest might be relying on hunting regulations (Smith & Reynolds 1992, Menuet al. 2002, Otis 2004, United states Fish and Wildlife Service 2008). One regulation type open toUsa states are split hunting seasons, the location where the hunting months are split up into 2 ormore segments (Ladd et al. 1989). The Usa Fish and Wildlife Service first offered the split-seasonoption to all United states states in 1948 (Ladd et al. 1989), and also the mid-1980s, approximatelyhalf of the states in the United states adopted split hunting seasons (Baldassarre & Bolen 2006). Theintention of split hunting seasons is usually to increase hunter success and opportunity by betterallocating hunting days to match waterfowl migrations via an area and by restoring waterfowlnaivety to hunting pressure during non-hunting periods (Baldassarre & Bolen 2006). However, theefficacy of split hunting seasons merely has been investigated a little bit and the relationship ofoverwintering waterfowl survival to periods of time within the hunting season is hidden.

Previous research has found hunting to become the primary source of waterfowl mortality throughthe overwintering season (Migoya & Baldassarre 1995, Cox et al. 1998, Fleskes et al. 2002, Fleskeset al. 2007), minimizing survival http://www.sniperaim.com/ has become documented during huntingperiods in comparison to non-hunting periods (Cox et al. 1998, Fleskes et al. 2002, Moon & Haukos2006). Additionally, Fleskes et al. (2007) found an inverse relationship between overwinteringsurvival of female mallards Anas platyrhynchos in centralCalifornia and USA, and the amount ofhunting days. Hunting decreases survival directly through hunter harvest and crippling, andindirectly through disturbance, which increases energy usage to result in waterfowl to protectyourself from more preferred roosting and feeding areas (Fox & Madsen 1997). With regards towaterfowl survival within hunting periods, waterfowl mortality continues to be documented to behigher with the onset of hunting periods (Longcore et al. 2000, Davis 2007, Fleskes et al. 2007),likely as a result of waterfowl naivety to hunting pressure and increased hunter participation. Otherstudies, however, have realized mortality from hunting to become under, or comparable to, otherreasons for mortality (Bergan & Smith 1993, Bielefeld & Cox 2006, Moon & Haukos 2006) and getobserved 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 afflicted with environmental body and factorscondition. Higher overwintering survival continues to be documented during several years ofincreased precipitation and much better habitat conditions (Migoya & Baldassarre 1995, Moon &Haukos 2006, Fleskes et al. 2007). Bergan & Smith (1993) found out that survival of female mallardswithin the Playa Lakes Region of northwesternUSA and Texas, decreased following severe varyingweather conditions (i.e. five days of [degrees]C with snow cover) as did Jeske (1991) for femalemallards from the San Luis Valley of Colorado, USA, particularly after snow accumulation whichreduced food availability. Patterns are less general, whilst the relationship between body conditionand overwintering survival has received much attention. Some reports have supported thehypothesis that better body condition increases overwintering survival and decreases inclinationtowards harvest (Hepp et al. 1986, Dufour et al. 1993, Heitmeyer et al. 1993, Robb 2002), whileother studies have not found this relationship (Jeske et al. 1994, Cox et al. 1998, Lee et al. 2007).Individuals in poor body condition maybe prone to be unpaired and therefore more easily interestedin decoys, more susceptible to disease, compelled to use habitats with greater hunting pressure andmuch less dedicated to predator and hunter avoidance as a result of spending additional time insearch of food (Hepp et al. 1986, Fleskes et al. 2002). Body condition of mallards is shown todecrease during cold temperatures events (Whyte & Bolen 1984, Robb et al. 2001). Coloradomallards can be more prone to mortality after severe weather as a result of low endogenous sniperscope energy stores (Jeske 1991, Dugger et al. 1994).

Uncertainty exists for the standards affecting overwintering waterfowl survival, with no study, to theknowledge, has empirically tested for effects linked to the opening of hunting periods. Given thisuncertainty along with the widespread application of split hunting seasons in the USA, we estimatedadult mallard daily survival rates over the South Platte River corridor in northeastern Coloradoduring September--February. We tested a priori hypotheses about variations in survivalbetweenyears and sexes, different non-hunting and hunting periods and time 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, ourcompany offers recommendations which may be employed by managers to affect overwintering

survival.

methods and Material

Study area

We conducted our study on the South Platte River corridor (i.e. [approximately similar to] 10 kmbuffer all around the South Platte River) in Sedgwick, Washington, Logan and Morgan counties innortheastern Colorado. Most bodies and wetlands water in these counties are inside the South PlatteRiver corridor. During 2005/06, the pilot study year, our study area included the South Platte Rivercorridor from Fort Morgan east for the Colorado-Nebraska state line, approximately 150 contiguouskilometres. During 2006/07 and 2007/08, two smaller study areas within the 2005/06 study areawere utilised. The eastern study area extended through the town of Sedgwick west towards the townof Iliff, approximately 56 km. The western study area extended from your town of Sterling west toSnyder, approximately 48 km. Natural vegetation is shortgrass prairie, dominantly grama speciesBouteloua spp. and buffalograss Buchloe dactyloides with cottonwoods Populus spp. occurring alongwetlands (Ringelman et al. 1989). Primary utilisation of the landscape is cattle production andfarming, 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 or

walk-in funnel traps during September-January, except that trapping started in late Novemberthrough the 2005/06 season. We measured body weight (g) and wing length (mm) upon capture,except during 2005/06 (N = 38), to calculate body condition index (BCI = weight/wing length;Ringelman & Szymczak 1985). We used backpack VHF radio-tags, which weighed approximately 25g (model A1820 manufactured by Advanced Telemetry Systems (ATS)). Battery was approximatelynine months. Radio-marked mallards were located with vehicle mounted Yagi antennas.Overwintering survival was monitored from 1 December-21 February during 2005/06, 15September-10 February during 2006/07 and 9 September-13 February during 2007/08.

During 2005/06, radio-marked mallards were found on average 3 times every day (range: 1-15) for 3-7 consecutive days separated by 1-15 events of no monitoring. During 2006/2007 and 07/08, radio-marked mallards were located 2-three times each day for about fourteen days separated by 3-19times of no monitoring. Radio-tags sending a mortality signal (i.e. signal doubled in frequency afterfour hours of inactivity) were recovered as soon as possible to determine reason behind death.Carcasses, when available, were inspected for indications of predation and hunter crippling (i.e.shotgun pellet wounds and shattered bones). We recorded mallards found dead from apparentcrippling and those reported harvested by hunters as hunting mortalities. All the other mortalitieswere recorded as non-hunting mortalities (often known as natural mortalities; see Bergan & Smith1993, 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 could be extended tomany other known-fate data such as radio-telemetry data, when marked animals are certainly notmonitored at regular intervals of time (Schwartz et al. 2006, Mong & Sandercock 2007), as were ourdata. We excluded all data from your first four days after radio-tag attachment in order to avoidemigration and mortality biases connected with radio, capture and handling-tag effects (Cox & Afton1998). Radio-marked mallards with no detectable signal inside our study area or those that wererecovered dead outside our study area were censored from the survival analysis in the before theywere located alive within our study area.

According to previous research, preliminary modeling as well as to keep the actual size of our modelset manageable, we included sex and a parameter designating hunting periods from non-huntingperiods in every models. We considered other variables to look at variation in mallard survivalrelative to year (2005/06, 2006/07 and 2007/08), different hunting periods (H), different non-huntingperiods (NH), time intervals within hunting periods (opening effect for starters, two or three weeks(1 WK, 2 WK and three WK), holiday effect (HOL), quadratic trend across time (T2), body conditionindex (BCI) and environmental factors (accumulated snowfall (SNOW) and daily minimumtemperature (TEMP); see Table 1 for descriptions). Temperature and precipitation data were

removed from the Akron 4 E, Colorado weather station (National Climatic Data Center 2008), theclimate station nearest to our study area.