Tuesday, May 30, 2017

More on Great Spirit Bluff

We are getting a lot of questions about the perch design at Great Spirit Bluff. Are falcons jumping because the perches are poorly designed? No - they are jumping because of an unusually early and intense (what we call explosive) - emergence of adult black flies.

Why are we so sure? The sites at which we have platforms (Xcel Energy's Allen S. King and Sherco plants, for example) don't have better production records than the sites at which we don't (every cliff site, sill-mounted sites at power plants, and stackhouse sites, to name a few).  Great Spirit Bluff didn't begin having problems until our first black fly hatch in 2013. As you can see below, the only exception was 2008, and I suspect we had a new female (probably Michelle's first year) because the nest chronology really went very late, shifted early the next year, and stayed early. We installed the nest box here in 2003, falcons adopted it in 2005, and we put it online in 2011. Here is what the record looks like. You can check it for yourself at http://www.raptorresource.org/about-us/annual-reports-and-papers/

  • 2005 - 4 falcons produced
  • 2006 - 3 falcons produced
  • 2007 - 3 falcons produced
  • 2008 - 1 falcon produced
  • 2009 - 4 falcons produced
  • 2010 - 4 falcons produced 
  • 2011 - 4 falcons produced
  • 2012 - 3 falcons produced
  • In 2013, we banded four young. All of them stampeded from the nest following a blackfly swarm. We recovered one from the ground below the cliff and transplanted him to a nestbox with two young of the same age. He survived and fledged just fine. Two other falcons must have survived and been fed by the parents, because they showed up at the nestbox one day, all feathered out and looking great. One probably died - we never saw it again and it hasn't turned up anywhere else yet.
  • In 2014, only one egg hatched. Watchers might remember that as a really brutal spring. We banded the lone male, but he stampeded from the nest box at about 30 days of age following a black fly swarm. We found him below the bluff with our cameras and monitored him as his parents cared for him. He fledged just fine. 
  • 2015 - 4 falcons produced
  • 2016 - 4 falcons produced
  • In 2017, two young falcons died following a black fly swarm. We recovered both carcasses, did a field examination on one (referencing 'Managing Peregrine falcon at the Eyrie' by Cade), and took the other into the U of MN for an autopsy. We are still waiting for the results from U MN. The one we examined had multiple bites along the edges of both wings, its wingpits,  the skin around its eyes, and its cere, It had a couple of bites (but not many) in its thighpits. There were no bites or sign of insects in its mouth, its nares, or its nasal passages. I did a field examination on the two survivors when we banded Sunday, and neither one of them were nearly as badly.
A couple of comments on 2017 - the swarm was earlier than we have ever seen it and we have never at ANY of our cammed sites seen young falcons venturing outside at roughly 17 days of age. Not on platforms. Not on bars. Not ever, not anywhere.

We are researching ways to design a box that will minimize black fly swarming and offer a slightly larger platform, but if this is a problem with the falcons we watch, it is also a problem for countless birds we can't see. It is time to start thinking about ways that climate change is impacting the birds we watch and love and the birds we love but can't see. If we don't recognize the problem or confine the problem only to what we can see, we can't make a difference.

So why do we think the falcons died? We are still waiting for autopsy results, but black flies are a vector for blood parasites that kill young birds with undeveloped immune systems. A link: http://www.arcticraptors.ca/pdf_docs/Arctic69-3-281.pdf. Whether or not you understand that climate change is linked to anthropomorphic activity, use your favorite search tool to learn about climate change, black flies, and mosquitoes, just to name a few. 

Tuesday, May 23, 2017

Black flies and falcon deaths at GSB

As watchers of Great Spirit Bluff know, we lost two falcons to what we suspect are a species of black fly/buffalo gnat. At this point, we believe that flies clogged the airways of the young falcons, suffocating them. We plan to collect the carcasses on May 24 for examination. Although none of us believe that the flies came from within the box, we'll take a sample of gravel for examination as well.

We've had black fly problems here in the past. In 2013 and 2014, young falcons were stampeded from the box in mid-June, when they were roughly 30 days of age. But that we know, we've never had a serious problem this early. Why are black flies swarming the box now? It is a more complicated answer than you might think.

Which black fly is this? There are 30 species of black flies in Minnesota, but not all of them are good candidates for this location. For example, it probably isn't Simulium johannseni (develops primarily in the Crow River) or Simulium meridionale (develops primarily in the Minnesota and Crow rivers), but ruling out those two still leaves 28 possibilities. Although black flies as a whole are grouped into one family (Simuliidae), black fly species have very different life styles.  It would be helpful to know which species we are dealing with.

What does its life cycle look like? From Purdue: "The length of time it takes an egg to hatch varies greatly from species to species. Eggs of most species hatch in 4-30 days, but those of certain species may not hatch for a period of several months or longer.  The number of larval stages ranges from 4-9, with 7 being the usual number.  The duration of larval development ranges from 1-6 months, depending in part on water temperature and food supply. The life cycle stage that passes though winter is the last stage larva attached underwater to rocks, driftwood, and concrete surfaces such as dams and sides of man-made channels."  In short, the eggs for the 2017 hatch were most likely laid in 2016. The larvae emerged somewhere between one month ago or six months ago. When I compared average April temperature and precipitation for the area for every year between 2013 and 2017, I found that April 2017 was the warmest, if not by much.

Average Temp (F) Average Precip (inches)
 April 2017 53 4.87
 April 2016 50 1.08
 April 2015 51 4.16
 April 2014 45 7.03
 April 2013 43 6.11

The complicated structure of black fly life means that we also need to look at the conditions last fall and winter, which were unusually warm and dry. Did more eggs and larva stay local given the lower river current? Did more larva survive given the unusually mild conditions? Did the slightly warmer April weather lead to an earlier season? Did sun and warm temperatures following days of cold and rain lead to an explosive hatch? John noted that the swarm seemed to blow up and fade very quickly. This video shows 'those dreaded flies': https://youtu.be/Rua_nnLF6TE

Can we control them?
We are looking into it, but we don't have an easy answer yet. We need something that doesn't volatilize since we can't descend to the box every day to spray it. It has to be strong enough to kill flies but not strong enough to harm hatchling and nestling falcons. It can't destroy the integrity of the box or let too much precipitation or wind in through the side. We are contacting the University of Minnesota's insect extension team to pick their brains and have also emailed Dr. Laura Johnson about safe possibilities. John and Susan had an intriguing idea about soaking mesh scrubbies in some known organic repellents and securing them in a safe location inside the nest box, so we may try that as well.

I wish we had more answers for everyone now. We'll do what we can and post more information when we have it.

Tuesday, May 02, 2017

A Peregrine falcon at the Decorah North Nest!

Peregrine falcon, Decorah North Nest
A sharp-eyed camera operator spotted an unbanded adult peregrine falcon at the Decorah North Nest this morning: https://youtu.be/HyVFISzaqOQ. What a surprise, especially given that there are no cliffs or large rock faces in the immediate area! As we've seen, the North nest is on a flyway of sorts. While almost all of the falcons we watch are on eggs right now, this could be a 'floater' - an unpaired adult falcon with no home territory. If we start seeing or hearing it on a regular basis, we'll need to figure out what it is doing in the area.

Although it isn't common, tree nesting has been documented in peregrine falcons in the United States as recently as 2013. The authors of the short communication Tree-Nesting by Peregrine Falcons in North America: Historical and Additional Records reviewed literature and found 33 North American records of peregrine falcons nesting in trees or snags in Alaska, Kansas, Illinois, Tennessee, Louisiana, Virginia, and British Columbia. However, their field research indicates that tree nesting could be more common than the literature suggests.

Of the 33 tree nests recorded between 1867 and 2007, nine were in tree cavities, nine were in the nests of other raptors (most commonly bald eagles), four were in bole 'platforms' created by a large tree breaking or snapping, and ten were unspecified. Of the nine nests found by the researchers between 1998 and 2013 in California and Washington state, six were in bole platforms, one was in a very large snag, and two were in bald eagle nests.

Peregrine falcons tend to imprint on nest sites, so would they be likely to cross over to trees on their own? The re-establishment of tree nesting peregrines in Europe didn't occur until fledgling peregrine falcons were tree-hacked in a process very similar to Bob's cliff release program. But peregrine falcons have taken over osprey nests with no assistance or direction in New York and New Jersey, and the breeding sites reported by Buchanan, Hamm, Salzer, Diller, and Chinnici are the first documented tree nests used by Peregrine Falcons in Washington and California, the first use of redwoods, Douglas-firs, and grand firs ever recorded, and the first reported snag use by peregrines in North America in over 60 years. As the authors state, Additional records of tree-nesting might
be expected if Peregrine Falcon populations continue to increase beyond levels already thought to have exceeded historical abundance (Ratcliffe 1993, Hayes and Buchanan 2002). Given the platform and tree nests in New York, New Jersey, California, and Washington state, it seems that peregrines can change their nesting behavior, although we don't know how likely they are to do so.

One appearance near a bald eagle nest does not make a tree-nesting peregrine population make, but a peregrine in an unexpected place is always exciting to see and we'll keep everybody posted!

Links
A quick end note: as many of you know, Bob identified the 'bird mounds' at Effigy Mounds (and other places) as peregrine falcons in part because they were shaped like peregrine falcons and in part because they were often located near historical peregrine eyries. His research on that can be read here: https://raptorresource.blogspot.com/2015/08/falcon-effigies-of-upper-mississippi.html. When Bob was asked about falcon mounds in places with no cliffs or falcons, such as the Five Hawks effigy mounds once located near Prior Lake, Minnesota, he replied that there had probably been tree-nesting peregrine falcons in the area when the mound builders were active. While we can't know for sure, it is wonderful to think that there may have been tree nesting peregrines in Minnesota, Iowa, and Wisconsin a very long time ago.