Why Doesn’t the Spring Season Open Earlier in Pennsylvania?
Mary Jo Casalena, PGC Gamebird Section, Bureau of Wildlife Mgmt., May 2019
Pennsylvania’s 2018-2027 Wild Turkey Management Plan (WTMP) specifies a statewide month-long spring gobbler season opening the Saturday closest to May 1, plus a ½ day statewide youth-only hunt the Saturday prior to the regular season opener (Table 1). Spring season structure (opening date placement and overall length) was addressed in the WTMP because it has the potential to significantly impact wild turkey populations via hen mortality / disturbance, and gobbler harvest rates.
Hen Mortality and Disturbance: A common request from spring turkey hunters is to open the season earlier to hunt during the first peak of gobbling and/or prior to spring “green-up”. These may vary from one part of Pennsylvania to another. A more important determinant of proper season timing is the date of the average peak of nest incubation (as with most game birds, turkeys lay individual eggs over a period of about 2 weeks, but do not begin incubating until the full clutch is laid, which results in synchronous hatching and all young being ready to leave the nest soon after hatching). Why is this date important? During egg-laying, hens are more active, move more extensively, and are more sensitive to disturbance than during incubation period. Consequently, they are much more susceptible to illegal harvest and nest abandonment, both of which have direct negative effects on reproduction (and thus, future populations). Though spring hen disturbance and mortality can never be completely eliminated with >200,000 hunters afield, initiating this level of hunting activity prior to the peak of incubation greatly increases the risk.
A variety of factors influence the start of breeding and egg-laying for turkeys, but photoperiod (day length) is the main trigger. Other factors that influence hormonal changes are weather, precipitation, food abundance, breeding density, and body condition, but increasing photoperiod is the primary cue for gonadal maturation and release of hormones during spring. Of 254 hen turkeys with satellite transmitters monitored from 2010-2014, median incubation initiation date was May 2. This was 2 days earlier than the median date during a 1953-1963 Pennsylvania study. However, during both studies, incubation initiation varied greatly among years and individual hens. From 2010-2014, the maximum proportion of hens beginning incubation typically varied by several days (2010 and 2012) to >1 week (2011, 2013 and 2014). During 4 of those 5 years the spring season opened 3 to 8 days prior to median date of incubation initiation. Due to the spring season structure of opening on the Saturday closest to May 1 and annual variation in incubation initiation, opening the season near the long-term median date of incubation initiation exposes few additional hens to risk, and hunter satisfaction is likely maintained at greater levels than would be seen with a more conservative approach of opening the season later.
Gobbler Harvest Rates: Another benefit of opening spring turkey season in conjunction with the average peak of incubation is, with most breeding complete, a relatively high proportion of males can be removed from the population without impacting reproductive output (hens can lay 2 complete clutches of fertile eggs after only 1 successful breeding). Maintaining adult gobbler harvest rates of < 50% is an important social issue to maintain enough adult gobblers for hunter satisfaction of hearing, calling, and harvesting adult gobblers. Adult gobbler harvest rates in Pennsylvania averaged about 40% during a 2006-09 study.
Pennsylvania Spring Seasons Compared to Surrounding States: Several surrounding states open their spring seasons 1-2 weeks earlier than Pennsylvania, but it is important to note that our hunter numbers, gobbler harvest rates, and total spring harvests – and thus the potential negative effects of opening too early - are far higher. New York comes the closest to matching our hunter numbers and harvests; there, the spring gobbler season is a fixed May 1-31 timeframe (31 days of hunting annually). Although the absence of Sunday hunting in Pennsylvania results in 1-6 fewer days to hunt than New York overall each year, our opening date under the WTMP guidelines averages out to be the same – a few days earlier in some years, a few days later in others. (Because a constant May 1-31 structure would only provide 4 Saturdays some years, varying the opening date around May 1 maintains 5 Saturdays in the season). Pennsylvania’s fall harvests (and thus the level of additive hen mortality we must account for) are also much higher than surrounding states, which increases the importance of setting our spring season appropriately.
Conclusion: Pennsylvania’s wild turkey resource provides countless benefits to consumptive and non-consumptive users alike. Ensuring the long-term sustainability of these benefits requires careful consideration of the biological needs of wild turkey populations.
For additional information refer to the Pennsylvania Wild Turkey Management Plan, 2018-2027.
Table 1. Example of Pennsylvania spring gobbler seasons, 1994-2020.
Figure 1. Proportion of satellite-transmittered eastern wild turkey hens incubating eggs by day in Pennsylvania, 2010-2014. Shaded area represents duration of spring turkey hunting season (not including youth season), from earliest season opening date of the 5 years represented, 27 April, to latest closing date of 31 May.