Although the September teal season brings into focus the upcoming waterfowl season, it is also the time in which we reflect on the ducks that were produced on the area. We’ve been monitoring nest boxes at Duck Creek for 19 years. This has given us the opportunity to observe trends of the breeding wood ducks and hooded mergansers over time. Peter Blum has been the waterfowl biologist going out every day, tending the boxes, monitoring the eggs, and banding the ducklings year in and year out.
This year Peter monitored 103 nest boxes during the breeding season on Duck Creek. Overall 71 nests were started by either wood ducks or hooded mergansers. Interestingly, this was the lowest number of nest attempts recorded during the 19 year study. Out of these 71 nest attempts, a total of 1,005 eggs were laid by either species. At the end of the breeding season 727 ducklings had hatched out and left the nest boxes, which is about 100 less than the long-term average. Overall, it looks like a slow year with fewer nest attempts and a smaller number of ducklings produced, but there is a different story when you split out the wood ducks from the hooded mergansers.
Wood ducks attempted 49 nests and laid a total of 731 eggs in 2014. This was the lowest number of nest attempts and total number of eggs that has been recorded during this study. Half of these nests had been initiated by April 4th, which is almost a month later than hooded mergansers. Despite the low numbers and late start the nest success was 78%, which was better than the long-term average of 69%.
At the end of the season 466 wood ducks exited the nest boxes. Three hundred and eighty of these downy ducklings were sporting leg bands before they left the nest. Later in the summer 3 of these birds were recaptured in Pool 1 at the age of 71 and 72 days. Prior to re-release their legs and bands were inspected and look good. This is the third year in a row that the number of wood duck ducklings has decreased. Over the course of the study there typically has been a peak and a dip in numbers every four to five years. This recent downward trend in wood duck production has begun to break away from the up and down cycle that we’ve seen before.
Data on the breeding hooded mergansers at Duck Creek are similar yet different than the wood ducks. They too nested later in 2014 than previous years, as noted earlier in this post. Half of the hooded merganser nests had been started by March 9th. In 2013 this halfway date had been March 4th. In 2014 hooded mergansers made 22 nest attempts and laid a total of 274 eggs. They too were very successful with 91% of the nests resulting in hatched ducklings, which is much higher than the long-term average of 75% nest success.
All but one hooded merganser duckling hatched and left the nest box with some leg jewelry, totaling 260 young hooded mergansers with leg bands. Twenty of these young mergansers hatched out of wood duck nests. You might recall hooded mergansers employ the strategy of nest parasitism which is laying eggs in another hen’s active clutch so that it doesn’t have to raise its own brood. Results over the years from this study have shown that this is a successful strategy for hooded mergansers as they haven taken advantage of the active wood duck nests. Another difference in the long-term trend for the hooded mergansers has been the steady increase in duckling production. For the first half of the study period the average number of hooded mergansers that left the nest was 93 birds. In the last ten years the average has been over double that amount with the last 5 years being between 241 and 271 ducklings.
The reason for the three year decline in wood ducks and uptick in hooded merganser production is unknown. Possible explanations include that it is part of the natural variability of population dynamics, somehow tied to harvest of local birds later in the fall, or perhaps wood ducks are using natural cavities at a higher rate in recent years while the mergansers are keying in on the boxes. We’ll just have to stay tuned and see what happens in the coming years.
There are a couple of online resources that are good to know if you find banded waterfowl interestng. First of all, if you happen to harvest a banded bird, please do your part to contribute to science and our understanding of these birds by reporting the band at www.reportband.gov. Secondly, if you want to explore recovery locations for different species of banded waterfowl in particular flyways or states go to Bands Across North America. It is worth checking out.