From: Rex Rowan <rexrowan@gmail.com>
To: Alachua County birding report
The good news is that Steve Goodman and Sam Ewing, participating for the first time in Georgia’s Youth Birding Challenge, won the first place trophy today (!!!!): https://www.flickr.com/photos/74215662@N04/17281902992/ Congratulations, guys! WE knew you were great birders, now everyone else does too!
Other good news: Backyard birding is getting more interesting. Just today, Becky Enneis had a Wood Thrush at her place in Alachua, Dana Griffin had an Ovenbird in his NW Gainesville backyard, and Ron Robinson photographed a Summer Tanager and a Black-throated Blue Warbler in his Back Yard De Luxe west of Gainesville.
Now the bad news: UF wildlife biology professor Dr. Peter Frederick, who has been observing the nesting colonies at Seahorse Key over the past few years, has reported a complete abandonment of nesting activity on Seahorse Key that seems to have occurred within the past two weeks. He gave me permission to publish his report, but he had some cautions: “I am very concerned about speculation and blame in the absence of much evidence and I hope that you will emphasize that there are still many possible explanations for what happened, some of which are natural causes. Please remind the readers that in the 1930s the birds bred predominantly on Snake Key and that colonies can be very dynamic.” With that said, here’s Peter’s report from the 25th:
“We learned a lot today about the loss of nesting at Seahorse, though we do not have a conclusive explanation for events. The synopsis is that Maria and Kenny were right – there has been a complete abandonment of all nesting at Seahorse, and many of those birds have apparently begun nesting at Snake Key. The cause of abandonment is unclear, though we think we can rule out one or two of the potential stressors.
“First, the Seahorse Key trip, in which we walked over large portions of Gardiners Point, revealed no active nesting of any species aside from ospreys on their platforms. Cormorants, Pelicans, ibises, egrets, herons, spoonbills – all are gone. Vic had recorded very typical flight line counts only two weeks ago and I had heard that Larry Woodward may have seen evidence of nesting even more recently. We found nests that were falling apart with no eggs or chicks, and hundreds of eggs on the ground, nearly all of which had been opened by Fish Crows. The characteristic marks of avian egg puncture (shell edge pushed inwards, intact hemispheres of eggs) are easy to tell from raccoon marks (crushed eggs, teeth marks) and we only found one or two eggs that might have been handled by a raccoon. All of this could well have been scavenging rather than direct egg predation. We also saw the remains of up to 15 dead cormorants, five dead pelicans, two dead ibises, three dead black-crowned night herons, and one dead fish crow. We estimate that there must have been many more dead birds – we did not cover the entire island or the entirety of Gardiners Point.
“Its unclear if the numbers of dead birds are abnormal – all breeding aggregations of birds have dead individuals lying about. I thought the number was excessive for normal mortality, though there was disagreement on this point by Marilyn Spalding, who has also been in a lot of colonies. The mortalities all seemed to be roughly the same age though, and many still had beetle larvae on them that may help us to define the rough time of death, CSI style. We collected about seven of the carcasses, and though all were bones and feathers, no flesh, there may be important information to be had from them. The synchronicity of the mortalities is also atypical of most healthy colonies.
“All signs pointed to a mass abandonment of nests that was at least roughly synchronous. The fact that so many species abandoned at once makes interruptions in many different food supplies at once unlikely as an explanation – so does the fact that nearly all species appear to have re-initiated nesting on Snake Key. The lack of evidence of raccoon bite marks on eggs suggests that raccoons were not the primary source of nest abandonment. We found no raccoon tracks on the beaches of Gardiners Point and found only one scat in the interior of Gardiners Point – it did not appear to have shell fragments or feathers in it. We walked the entire gulf-facing beach front on Seahorse and found tracks on the southeast part, suggestive of one or perhaps two individuals. Since Fish Crows cannot usually intimidate birds off their nests, their eating of eggs looks entirely secondary to the abandonment – the crows were scavenging abandoned eggs. The fact that the birds have re-initiated on Snake Key strongly suggests that something occurred at Seahorse that was hugely incompatible with nesting there, and frightened all the birds off.
“There are several possibilities for the cause. Eagles could have begun attacking adult nesting birds – this has caused mass abandonment before in seabird colonies, and the placement and skeleton evidence suggests that the carcasses we found could have been eaten by a raptor. However, they could also have been cleaned off by crabs or rats or beetle larvae and the evidence might have looked very similar. Eagles are common at Seahorse, but they have coexisted with birds there for some years and at other colonies elsewhere in coastal situations for some years. Snake Key has a resident pair – if the birds were flipped out by predatory eagles it seems unlikely they would have chosen Snake to re-nest.
“Human disturbance that included killing through shooting or some other mechanism could also be a possibility. The placement and disposition of the dead birds could have been from birds that were shot. There were many more carcasses on the edge, particular the north end of Gardiners Point, than in the middle. Thus someone with a gun might have been shooting birds from a boat, creating this pattern. The carcasses we collected should allow us to tell whether they were shot – usually there are marks on bones that indicate the passage of lead shot, though this is easier to tell with shotgun than with single shot. We also found no shell casings despite some pretty intensive looking-down to avoid the cottonmouth moccasins. Similarly, predation by eagles has characteristic talon marks that often puncture the back of the head. So I believe it would be of great value to get the carcasses analyzed by some lab that can do decent forensics. While it seems farfetched that someone would do such a thing (and even more, that no one would hear or see it), remember that we have probably gone two weeks without noticing that the birds had abandoned – so our detection and monitoring is episodic, and such an event could well have occurred.
“We did find large numbers of all the species except ibises nesting on Snake Key, nearly all on the north side. We saw one pelican apparently on a nest and many others building and courting. I counted 65 cormorant nests and over 150 individuals, many of which were carrying nesting material. We saw Roseate Spoonbills carrying nesting material and descending with it into the mangroves on the north side, and at least two Great Egrets carrying nesting material and displaying high courtship colors on the nares. In short, everything that abandoned at Seahorse was at Snake, starting anew, albeit probably in smaller numbers. Note that this section is being monitored by trail cameras set on poles looking towards the island, and these cameras should have been able to document the buildup of birds there – which may help us pinpoint the timing of the abandonment at Seahorse.
“We may never know what happened on Seahorse – but it is unprecedented in the history of the island as far as I or anyone else on the trip today knew. While the past numbers of nests have fluctuated, there is no record of zero in recent history, especially by all species. This could be temporary, and the birds might return to Seahorse next year, or it could be permanent, especially if they do well at Snake this year. Given the numbers of birds at Snake, it seems appropriate to put up no entry postings as they have been at Seahorse, since in my experience human disturbance from beachgoers and fishermen could be detrimental to nesting – but those are agency decisions to make.
“My experience with other colony abandonments is that we humans tend to jump to conclusions, and usually blame humans for such events, especially in the absence of evidence. Before we do so, I think we should at least get the carcasses analyzed. Until that time, I suggest that we ought to repeat that the abandonments at Seahorse appeared to be synchronous within the last two weeks, and the events leading to that abandonment are unclear. Interruptions in the food supply seems like the least likely explanation at this point, and investigations are ongoing. We should encourage anyone with observations about the nesting at seahorse to contact the Refuge. We should also appeal to the public to keep at least 100 meters away from the shores of Snake Key on all sides to give the birds a chance to re-nest. Given the late start of nesting there, it will probably be necessary to keep disturbance to a minimum well into July.
“I have probably missed important points in this whole description, and so encourage everyone to add information if they can.”
I wonder what will happen to the famous Seahorse Key cottonmouths, which survive on dead fish that fall from the nests. They’ll have a long wait between now and next spring, if the birds even return next spring.