Monday, October 4, 2021

October 2, 2021 - Fall Diversity - Kate Sutherland

Hurricane Sam was passing to the east of Bermuda over the weekend giving us just a bit of uncertainty about how much swell would reach us here in Hatteras and if it would cause any trouble for us getting across the bar and to the sea via Hatteras Inlet.  We were very happy to find things were quite nice for us to get out on Saturday with a long period easterly swell and north easterly winds setting us up for some good  conditions for seabirding!  Reports of shearwaters on the shelf had us searching the horizon as we headed offshore.  Around 0830 we found a nice flock of over a hundred shearwaters giving us the opportunity to show everyone Cory's, Scopoli's, Great,
and Audubon's Shearwaters sitting on the water and in flight!  The shelf came and went around 0930 and we started dripping some oil, but it took a little while for us to find our first Black-capped Petrels in the deeper water.  They seemed to be mostly sitting around early and we kept seeing small groups suddenly appear in the air around us.  Once we slowed and put more chum out, Wilson's Storm-Petrels found the slick and Black-capped Petrels started checking it out as well.  The Gulf Stream current was moving about 2-3 knots and with the wind against it, seas were a bit choppy in addition to the longer period swell from Hurricane Sam.  Sargassum, the brown algae with air bladders that is a typical feature of the Gulf Stream, was scattered around which meant Audubon's Shearwaters were out there and we had some nice views of these small black and whites offshore.  Just a handful of larger shearwaters were in the deep in contrast to the shelf waters, but that's okay because we had Black-capped Petrels out there! 
They were really showing off on Saturday and we had a number flying incredibly high before swooping down toward the sea.  Many times there would be two or three in a group arcing up into the sky before flying down one after another.  Our following group grew over the course of the morning and we had eight or nine back in the slick when I saw them chasing what looked to be a larger, pale bird way back behind us.  We circled back to get a better look and a pale Northern Fulmar came flying toward the boat!!  With a few Black-capped Petrels in tow.  
It was interesting to see the Black-cappeds exhibiting this behavior for a fulmar, because we typically see them harassing dark jaegers and skuas in this fashion.  A few petrels flying up behind the target bird and coming close, but not making contact, before veering away.  As many as six or seven Black-cappeds would work together to chase the fulmar, seeming to harass it and encourage it to leave the area. 
But, in true scrappy fulmar style, this bird was not deterred, and stayed with us feeding in the slick for almost an hour and a half!  Since we have seen larger birds like skuas feeding on dead Black-capped Petrels at sea in the past, we thought this behavior was akin to mobbing, a way to ward off a bird that is a threat to them.  But is it possible this behavior could be related to food?  A Black-capped Petrel exhibiting kleptoparasitism on Red-billed Tropicbirds was observed in the Cape Verde Islands recently (Peter Stronach personal comm).  It was pursuing these tropicbirds like a jaeger would until they dropped some food which the petrel would take.  The fulmar was larger than the Black-cappeds, so perhaps size could be a trigger for this behavior as opposed to coloration?  But we see them charge young Sooty Terns and Long-tailed Jaegers as well and Peter Flood photographed one pursuing an Audubon's Shearwater, all of which are slighter or smaller than a Black-cap.  We also regularly see them chasing one another around and Saturday we heard them calling as they fed on some chum together in a small group.  I imagine this behavior is more complicated than we know and we hope to compile all of our interactions into a note soon.
Once we got back to the shelf in the afternoon activity died down a bit so we picked up some speed to head back to the inlet.  As we were running along some of our participants saw what looked like a jaeger back at 0500, some distance from the boat.  Brian turned around to check it out and we found quite a nice little condition with some Sargassum and a number of birds!!  A young Long-tailed Jaeger was the bird that got our attention first and as we watched it it flew up into the sky in pursuit of something...
that was a young Sabine's Gull!!!  WOW!  The gull was obviously in distress as it tried to avoid the slightly larger jaeger on its tail, and it quickly disappeared into the sky presumably after giving up its last meal for the jaeger.  There were some cooperative Red-necked Phalaropes on this change and a number of Cory's type, Great, and Audubon's Shearwaters as well!  What a treat for the end of the day!  We have two more trips this fall, so hopefully this diversity will continue.
Thank you to everyone who joined us this weekend and thanks to Ed Corey for helping us to lead the trip!  Always a joy!  Photos in the post today are all mine - we might add some from Ed next week.

Species List for October 2, 2021
Northern Fulmar - 1
Black-capped Petrel - 58 to 71
Cory's Shearwater - 11
Scopoli's Shearwater - 11
Cory's / Scopoli's Shearwater - 216
Great Shearwater - 24
Audubon's Shearwater - 34
Wilson's Storm-Petrel - 60
Red-necked Phalarope - 7
Sabine's Gull - 1 immature
Long-tailed Jaeger - 1 immature
jaeger species - 1
Herring Gull - 3
Bottlenose Dolphin (Offshore population) - 11 to 12

Also seen on the shelf:
Lesser Black-backed Gull - 1
Laughing Gull - 24 to 26
Common Tern - 103
Atlantic Spotted Dolphin - 7

First, a few more images of the Black-capped Petrels and Northern Fulmar...
Black-capped Petrels were looking pretty sharp out there!
This one feeding on some chum looks to have a hole in the webbing of its foot!
We had a number of Cory's Shearwaters out there but most of my photos were distant.  Here is a nice view of what looks like perhaps a male Scopoli's.
There were a number of Cory's types that were not obliging in showing their underwings!  But we had a great time watching them feed in the Sargassum.  This one has an Audubon's Shearwater that just dove next to it!
Great Shearwater showing off the inside of its mouth and how they are able to keep ahold of those fishes and squid they like to eat!
An Audubon's flying near some Sargassum on the shelf in the afternoon.  Tough light, but you can see the long tail with dark under tail coverts.
Wilson's Storm-Petrels were super obliging during the offshore portion of the day showing off their long legs and even the yellow webbing on their feet!
One of the flyingfish that we encountered!  This individual doesn't seem to show dark pectoral fins like a blackwing flyer (Hirundichthys rondeletii), but otherwise looks quite similar to one.  Always interesting to see, photograph, and attempt to identify these awesome fishes!

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