Post by dcheckman on Apr 20, 2014 12:20:27 GMT -5
When do our turkeys nest?
By Bob Eriksen, NWTF Regional Biologist
PA Chapter NWTF "Turkey Talk" Winter 2014
The subject of the timing of wild turkey nesting is one that comes up regularly in discussions with turkey hunters. Avid spring gobbler hunters are out scouting in February and March. They find some mornings quiet and some mornings boisterous, filled with gobbling and hen talk on the roost. While winter flocks are intact wild turkeys can be extremely vocal. Gobblers can be seen displaying in snow covered fields. In fact, gobblers can be seen displaying almost any time but that does not mean there is any breeding taking place. By early April flocks are breaking up and given good weather conditions gobbling can be quite intense. After listening to gobbling activity while pre-season scouting some spring hunters become convinced that breeding and nesting are on the downhill slide by the time the spring season opens. They may have even observed breeding activity as early as the first week on March. Those observations help to solidify the theory that the curtain has come down on the best gobbling activity by the time our spring season opens.
Back in the 1990’s a researcher at Virginia Tech requested data on gobbling activity, nest initiation dates and nest incubation dates from wildlife agencies all over the country. Darroch Witaker was working on a PhD in wildlife science and his doctoral research was focused on documenting differences in nesting phennology (timing) at different latitudes (north to south) and at different altitudes. His goal was to estimate the best time to schedule spring gobbler hunting seasons and determine what states were closest to having a properly timed spring season. The data he collected from wildlife agencies varied according to what the agency had in its files. It ranged from casual observations to intense data on gobbling collected from survey routes and telemetry data collected by monitoring nesting hens. There was a ton of information. Dr. Witaker and other researchers poured over the data and began a very detailed analysis.
One data rich part of the country was the mid-Atlantic region from the Virginias to New York. There was gobbling tom survey data from New Jersey and Maryland providing some information about gobbling intensity. More importantly observations by experienced biologists and radio-telemetry studies documented nest initiation and incubation dates for Virginia, West Virginia, Maryland, Pennsylvania, New Jersey and New York. The difference between nest initiation dates and incubation dates is this: it takes about two weeks for a hen to lay a clutch of eggs and she does not incubate until she is finished laying. For example if she lays her first egg on April 22nd and lays a clutch of ten eggs it will not be complete until May 2nd. Therefore the nest incubation date would be May 2nd or 3rd. Data from those six states indicated that most wild turkey hens began laying in mid-April and the bulk of incubation began on the last day or two of April or in early May. Based on these data the authors concluded that spring gobbler seasons in the region should ideally open in late April or early May. The two states with the best timed seasons in the region were Pennsylvania and New York. The other states opened their season earlier than the ideal.
What difference does it make whether or not the season opens too early? Some hunters contend that the best gobbling happens before the season opens here in Pennsylvania and believe that they should be able to take advantage of those golden days of gobbling activity. Here’s the rub. If the spring season opens before most of the hens are almost finished laying eggs or starting to incubate, the chances of disturbance causing hens to abandon nests increases. Perhaps more important is the fact that hen mortality due to accidental or illegal kill by spring hunters increases if hens are not far along in incubation. While beginning to nest and lay eggs hens are more active than when they begin to incubate. That activity can make them more vulnerable. Studies in Missouri, Virginia and West Virginia showed that more hens were accidentally or illegally killed by hunters when the season opens early. Pennsylvania has a huge number of spring gobbler hunters. No matter when all of us take to the woods there is risk of some turkey hens abandoning their nests. The risk would increase dramatically if the season were to open too early.
How can we be certain the dates for nest initiation and incubation are accurate? Have they changed any in the past decade or two? Data used in the Virginia Tech study was collected from the 1960’s through the 1990’s. Nest timing data from Virginia, West Virginia, New York and New Jersey was collected using telemetry in the early 1990’s. The data on turkey nesting in Pennsylvania used in that study was from the 1950’s and 1960’s. How can we be sure nothing has changed?
Fortunately there is recent data to review. Game Commission data collected from 1953-1963 indicated that the average statewide date when hens began to incubate was April 28. From 1999 through 2001 the Pennsylvania Game Commission conducted a study of turkey populations on and around Michaux State Forest in Adams, Franklin and Cumberland Counties. Radio-tagged hens were monitored and the start of incubation among marked hens in that study was May 10. Of course that study took place in southern Pennsylvania. Is there a difference between egg-laying and incubation dates south to north in the Commonwealth? Do hens in the southern counties nest earlier? Should we have a “split season” opening earlier in the southern part of the state?
Current data collected from the on-going hen survival and fall harvest rate study sheds some light on that subject. The study will ultimately produce five years of nesting data. So far the study indicates that there is no difference south to north in the dates when hens equipped with satellite telemetry transmitters begin incubating nests. The median start date for incubation from 2010-2012 in the current study was April 29 and was similar in the northern counties to the dates in the southern counties. The conclusion is that nesting dates have not changed over more than half a century. Nor do the dates differ from south to north. This makes sense given that wild turkey nesting behavior is largely a factor of photoperiod (the number of hours of daylight). As daylight length increases in the spring hen turkeys are stimulated to breed and lay eggs.
The bottom line is this: spring gobbler hunting seasons in Pennsylvania are properly timed. The Management Plan for Wild Turkeys in Pennsylvania calls for the season to open on the Saturday closest to May 1. That is a safe time for the season to open based on nest incubation dates documented over a long period of time in the state. Our wild turkeys nest in mid to late April and May. Turkey poults hatch in late May through early June. Late nesting hens and hens that have lost a clutch of eggs hatch brood even later into July. On occasion hen turkeys have been known to hatch broods as late as August and September.
In order to assure a stable wild turkey population we biologists tend to approach spring season timing conservatively. That is our responsibility. Remember though that we are spring hunters too. While we would be pleased to hunt gobblers any time our job is to provide that opportunity for hunters with minimal impact on the future resource. Timing the season opener properly is essential to good management of our valuable wild turkey resource.
Courtesy of NWTF
By Bob Eriksen, NWTF Regional Biologist
PA Chapter NWTF "Turkey Talk" Winter 2014
The subject of the timing of wild turkey nesting is one that comes up regularly in discussions with turkey hunters. Avid spring gobbler hunters are out scouting in February and March. They find some mornings quiet and some mornings boisterous, filled with gobbling and hen talk on the roost. While winter flocks are intact wild turkeys can be extremely vocal. Gobblers can be seen displaying in snow covered fields. In fact, gobblers can be seen displaying almost any time but that does not mean there is any breeding taking place. By early April flocks are breaking up and given good weather conditions gobbling can be quite intense. After listening to gobbling activity while pre-season scouting some spring hunters become convinced that breeding and nesting are on the downhill slide by the time the spring season opens. They may have even observed breeding activity as early as the first week on March. Those observations help to solidify the theory that the curtain has come down on the best gobbling activity by the time our spring season opens.
Back in the 1990’s a researcher at Virginia Tech requested data on gobbling activity, nest initiation dates and nest incubation dates from wildlife agencies all over the country. Darroch Witaker was working on a PhD in wildlife science and his doctoral research was focused on documenting differences in nesting phennology (timing) at different latitudes (north to south) and at different altitudes. His goal was to estimate the best time to schedule spring gobbler hunting seasons and determine what states were closest to having a properly timed spring season. The data he collected from wildlife agencies varied according to what the agency had in its files. It ranged from casual observations to intense data on gobbling collected from survey routes and telemetry data collected by monitoring nesting hens. There was a ton of information. Dr. Witaker and other researchers poured over the data and began a very detailed analysis.
One data rich part of the country was the mid-Atlantic region from the Virginias to New York. There was gobbling tom survey data from New Jersey and Maryland providing some information about gobbling intensity. More importantly observations by experienced biologists and radio-telemetry studies documented nest initiation and incubation dates for Virginia, West Virginia, Maryland, Pennsylvania, New Jersey and New York. The difference between nest initiation dates and incubation dates is this: it takes about two weeks for a hen to lay a clutch of eggs and she does not incubate until she is finished laying. For example if she lays her first egg on April 22nd and lays a clutch of ten eggs it will not be complete until May 2nd. Therefore the nest incubation date would be May 2nd or 3rd. Data from those six states indicated that most wild turkey hens began laying in mid-April and the bulk of incubation began on the last day or two of April or in early May. Based on these data the authors concluded that spring gobbler seasons in the region should ideally open in late April or early May. The two states with the best timed seasons in the region were Pennsylvania and New York. The other states opened their season earlier than the ideal.
What difference does it make whether or not the season opens too early? Some hunters contend that the best gobbling happens before the season opens here in Pennsylvania and believe that they should be able to take advantage of those golden days of gobbling activity. Here’s the rub. If the spring season opens before most of the hens are almost finished laying eggs or starting to incubate, the chances of disturbance causing hens to abandon nests increases. Perhaps more important is the fact that hen mortality due to accidental or illegal kill by spring hunters increases if hens are not far along in incubation. While beginning to nest and lay eggs hens are more active than when they begin to incubate. That activity can make them more vulnerable. Studies in Missouri, Virginia and West Virginia showed that more hens were accidentally or illegally killed by hunters when the season opens early. Pennsylvania has a huge number of spring gobbler hunters. No matter when all of us take to the woods there is risk of some turkey hens abandoning their nests. The risk would increase dramatically if the season were to open too early.
How can we be certain the dates for nest initiation and incubation are accurate? Have they changed any in the past decade or two? Data used in the Virginia Tech study was collected from the 1960’s through the 1990’s. Nest timing data from Virginia, West Virginia, New York and New Jersey was collected using telemetry in the early 1990’s. The data on turkey nesting in Pennsylvania used in that study was from the 1950’s and 1960’s. How can we be sure nothing has changed?
Fortunately there is recent data to review. Game Commission data collected from 1953-1963 indicated that the average statewide date when hens began to incubate was April 28. From 1999 through 2001 the Pennsylvania Game Commission conducted a study of turkey populations on and around Michaux State Forest in Adams, Franklin and Cumberland Counties. Radio-tagged hens were monitored and the start of incubation among marked hens in that study was May 10. Of course that study took place in southern Pennsylvania. Is there a difference between egg-laying and incubation dates south to north in the Commonwealth? Do hens in the southern counties nest earlier? Should we have a “split season” opening earlier in the southern part of the state?
Current data collected from the on-going hen survival and fall harvest rate study sheds some light on that subject. The study will ultimately produce five years of nesting data. So far the study indicates that there is no difference south to north in the dates when hens equipped with satellite telemetry transmitters begin incubating nests. The median start date for incubation from 2010-2012 in the current study was April 29 and was similar in the northern counties to the dates in the southern counties. The conclusion is that nesting dates have not changed over more than half a century. Nor do the dates differ from south to north. This makes sense given that wild turkey nesting behavior is largely a factor of photoperiod (the number of hours of daylight). As daylight length increases in the spring hen turkeys are stimulated to breed and lay eggs.
The bottom line is this: spring gobbler hunting seasons in Pennsylvania are properly timed. The Management Plan for Wild Turkeys in Pennsylvania calls for the season to open on the Saturday closest to May 1. That is a safe time for the season to open based on nest incubation dates documented over a long period of time in the state. Our wild turkeys nest in mid to late April and May. Turkey poults hatch in late May through early June. Late nesting hens and hens that have lost a clutch of eggs hatch brood even later into July. On occasion hen turkeys have been known to hatch broods as late as August and September.
In order to assure a stable wild turkey population we biologists tend to approach spring season timing conservatively. That is our responsibility. Remember though that we are spring hunters too. While we would be pleased to hunt gobblers any time our job is to provide that opportunity for hunters with minimal impact on the future resource. Timing the season opener properly is essential to good management of our valuable wild turkey resource.
Courtesy of NWTF
