Thanks to all of those that responded to my RFIs regarding American Bitterns and the egg id. I think I sent a personal thank you to everyone already, but I may have missed one or two. 100% said Killdeer egg.
With the start of summer some changes are being made to the accessibility of many of the sites I've been reporting about. Until further notice, all impoundment berms are now closed to unauthorized vehicles. Walk-in access is still allowed and, with enough advanced notice, drives around the berms may be coordinated by Heidi Hughes of the Agassiz Audubon Center ( [email protected]). The only impoundment that still has driving views is the AO#4 impoundment which is surrounded by public road. Additionally, the Agassiz Audubon Center will begin enforcing parking regulations and visiting hours beginning June 1st. Parking is $5 per vehicle and the grounds are open to the public only between 9 AM and 5 PM. Members of Agassiz Audubon can park for free, but this exemption does not apply to MOU members or members of Minnesota Audubon. If you have any questions feel free to contact me or Heidi. Most things should go through her. I should only be your contact for recent sightings. Regarding the American Bittern question about aerial courtship displays/flights/chases: I based the question off of two observations (now three) of American Bitterns chasing apparently smaller ones through the air. One of these chases involved quite a bit of circling and some fancy footwork that struck me as possibly being an aerial display that I was previously unaware of. I then stumbled onto several references to the existence of a courtship flight published in the Breeding Bird Atlases and DNR pamphlets of several states, none of which went into any detail. After looking into it further with the help of MOU's Anthony Hertzel, neither of us could find any scientific evidence to support such statements as: "Courtship behavior is not well understood, but is known to include aerial and ground chases." from the Massachusetts DFW ( http://www.mass.gov/dfwele/dfw/nhesp/species_info/nhfacts/botauruslentiginosous.pdf ) or "Courtship behavior, though not well known, includes aerial and ground chases..." from the Vermont Breeding Bird Atlas ( http://www.vtecostudies.org/vbba/pdf/VBBA1/american%20bittern.pdf) The two above sentences are remarkably similar, as are many of the other references I found. It seems to me that they are quoting each other rather than any particular study (many of them do not list sources). I think there has been a bit of snowballing misinformation stemming from a misinterpretation of this letter to The Auk in 1980 regarding a single observation of American Bitterns breeding: http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1056&context=biosciornithology Apparently the only aerial chases known to regularly occur between American Bitterns are between males as part of territory disputes, not between males and females as part of courtship. If anyone does know of evidence to support the existence of courtship flights for this species, I'd be very interested in learning more. For now, however, I am assuming I either imagined the size differences or witnessed larger, dominant males chasing younger/smaller ones off their territory. Thanks again to Anthony Hertzel for helping me piece much of this together. Bill Blackburn Minnesota Audubon Warren, MN ---- Join or Leave mou-net: http://lists.umn.edu/cgi-bin/wa?SUBED1=mou-net Archives: http://lists.umn.edu/archives/mou-net.html
