Monday, November 19, 2007

Jed Hayden, Marsh Bird Scientist

The "Previous Research Experience" of Jeremiah "Jed" Hayden's UMaine Wildlife Ecology Graduate Student section makes me very jealous. He's worked with saw-whet and boreal owls in Idaho, canvasback ducks in Nevada, the transmission of avian flu among ducks in Wisconsin, piping plovers on Long Island and other adventures that most birders wish they were doing instead of being stuck in an office somewhere.

From August 2004 through November 2006, Jed was in Maine researching the habits of secretive marsh birds for a Master's degree project. His project focused on long-term population trends of these birds in central and southern Maine. I asked him about his project with a focus on one particularly elusive Maine species, the Least Bittern.

Which marshes were you working in and what kinds of birds were you studying?

JH: I surveyed about 80 marshes (primarily freshwater) in southern and central Maine. I was re-visiting sites that had been previously surveyed in 1989-1990 or 1998-2000 to get an idea of how populations of marsh birds have changed in the last approximately twenty years.

The species I was looking at were Least Bittern, American Bittern, Sora, Virginia Rail, and Pied-billed Grebe. Results have shown that Least Bitterns have decreased substantially in the number of wetlands used. The surveys I did and similar ones done by Tom Hodgman at the Maine DIFW have shown the Least Bittern to be extremely rare in Maine. In fact it was recently listed as state "endangered." The other species appear to be doing quite well. American Bitterns and Virginia Rails have increased significantly and Pied-billed Grebes and Soras have not changed much at all.

It's interesting to me that Least Bitterns have decreased while American Bitterns have increased. To a birder but non-scientist, the birds seem to have very similar requirements in terms of habitat. Did you reach any conclusions as to why Least Bitterns are doing worse than their cousins?

JH: Any conclusions about the Least Bittern decline at this point are conjecture. However, through a habitat analysis that is also part of my thesis (along with a lot of field observations) it appears that American Bitterns are much less strict in terms of suitable habitat they will occupy. Least Bitterns seem to be only using cattail marshes with approximately a 50:50 ratio of vegetation to open water while American Bitterns are using these marsh types as well as marshes dominated by shrubs, marshes lacking much open water, and I even noticed that they will nest in uplands adjacent to wetlands.

It is certainly puzzling that the other species I studied are flourishing while Least Bitterns appear to be declining. Some of the possibilities in my opinion are: LEBI are on the edge of their range in Maine and this could be an effect of that, declines in the core population areas may be driving declines in the edges, and they migrate through and winter in areas that are still losing wetlands (eastern US coast, FL, LA, central America).

I wanted to look and see if American Bitterns may be competitively excluding Least Bitterns but did not have time. It is unlikely that this is happening because they tend to occupy different niches within a wetland, but I have had American Bitterns make aggressive movements when I presented them with LBI calls (very unscientific just my few field trials). Unfortunately my funding and time ran out, but the questions of why are they declining, and is this possibly a cyclical event, need to be answered. In addition, migration routes need to be identified to ensure protection.

Wow, what kinds of aggressive movements from the American Bitterns? Is this something they do with other marsh birds as well?

JH: I was studying two smaller marshes where AMBI were calling and no LEBI were present. Each time I went there, I would play the LEBI call and this would prompt the AMBI to fly over and start calling right away. It would not do this for other calls (i.e. SORA, VIRA). However there were a few marshes where both species co-existed so there may not be anything to this. It would be interesting to see if marsh size affected inter-species aggression (i.e. in large marshes with plentiful resources there is no aggression, but in small marshes with limited resources the two species won't tolerate each other). I have attached a picture of LEBI I took last year.

How would you determine whether not not Least Bittern were present? I imagine it would be tough (or messy, at least) to mist-net over a marsh...

JH: With all of these marsh birds the best way to determine presence is through a standardized callback survey. We set up points approximately 200 meters apart in each marsh and perform callback surveys at each point. Surveys are done between 1/2 hour before sunrise to 3 hours after sunrise to coincide with peak calling hours for the birds. I found the LEBI to be quite aggressive when present and had them come within a few feet of the canoe. I even had a Virginia Rail come onto the canoe. Mist-netting is messy in marshes, but it does work because the birds are so aggressive when defending territories.

Where in Maine (other than Scarborough Marsh) would a birder have the best chance of seeing Least Bitterns and what is the conservation status of those areas?

JH: Scarborough Marsh actually isn't a good spot. They were only seen once there and likely they weren't breeding. Some of the more reliable sites are Penjajawoc, Sand Point WMA in Stockton Springs, the North end of Sabattus Pond in the cattails, Belgrade Bog, a smallish cattail marsh on the east side of 95 (200 meters away from the highway) south of Hermon Pond on Bog Rd. There are a couple more I can't remember off hand. They are mostly protected wetlands, aside from the smaller one I mentioned last which I am unsure of.

What do you see as the future of Least Bitterns in Maine? Do you expect their small population to hold strong in protected areas or do you see their numbers continue to drop?

JH: I don't think LEBI were ever abundant in Maine, but they seem to be at historic lows currently. I hope they will at the very least maintain the small populations we are seeing now. The key is to identify sites they are breeding in and sites that contain suitable habitat and ensure these areas are sufficiently protected from development, pollution, etc. Long-term monitoring is also essential. It is possible we are at the low point in a population cycle and the population may increase in the future, but there needs to be annual surveys done to know what is happening for sure.


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