On Thursday, Central Park had a wonderfully cooperative Mourning Warbler. Usually, this species is very difficult to observe as it often is likes to hide in low vegetation. However, this bird out in the open and seemed to only be focused on finding worms to refuel before continuing its migration south.

Early low resolution photos send around on social media suggested the bird might be a similar species, a MacGillivray’s Warbler (whose range is in the west and Mexico), which has eye arcs rather than a broken eye ring. Adding to the puzzle was that this was a fall female-type (adult female or immature male), which is paler overall and has white in the throat, and not what many birders are used to seeing in Central Park.

So, birders got out their field guides and Warbler apps, and carefully looked for the differences in field marks between the two species. Beyond differences in eye rings, the yellow in the undertail tappers to a point in the MacGillivray’s Warbler rather than a more rounded blunt end in the Mourning Warbler.

So, upon closer inspection it was clear this was a Mourning Warbler but the exercise of confirming that it was worth the effort.

Ben Cacace has been documenting Chimney Swift roosting sites in New York this year, and one of the roosts he’s been watching is the old Christian Science Church at 96th and Centra Park West. On the NW corner of building is a chimney that can be seen from the east side of Central Park West or the south side of 96th Street. I watched the roost this evening from Central Park West.

Ben pointed out to me how unique this roost site is because the chimney is lower that the buildings that surround it.

The timetable of the evening was:

• 6:41 pm, First Chimney Swift enters the roost. a very small early group
• 6:42 pm, Sunset
• 6:45 pm, Chimney Swifts start gathering over the park, and then begin to circle the roost
• 6:55-6:57 pm, Large group enters the roost
• 7:01 pm, Last Chimney Swift enters the roost

The timing of when they roosted varied greatly from the 944 Fifth Avenue roost. Counting was harder with this roost. I could have over counted, as it as impossible to tell if the birds were overshooting the roost and going behind the chimney.

I was afraid that a new pipe on top of the Chimney Swift chimney on 944 Fifth Avenue meant the roost was sealed off and made the mistake of not waiting long enough to confirm that the roost was inactive last week. Luckily, Ben Cacace corrected me. At his suggestion, I made a video at 120 frames/second so the Chimney Swifts could be counted going to roost.

The schedule of the evening was:

• 6:44 pm, Sunset
• 6:45 pm, Chimney Swifts start circling the roost
• 6:58 pm, First Chimney Swift enters the roost
• 7:10 pm, Last Chimney Swift enters the roost

The swifts entered the chimney slowly, but then had one major burst around 7:01 pm followed by a much smaller burst a few minutes later.

Before a Linnaean Society of New York walk, Junko Suzuki found a Buff-breasted Sandpiper, the first record for New York County on Wednesday morning. This bird had stopped on its migration route from the High Arctic of Alaska and Canada to South America. Buff-breasted Sandpipers forage in short grasses, so the playing fields in the NE section of the island were a perfect place for this bird to stop.

Up by the Compost Heap is a Red-bellied Woodpecker nest. Today, I was lucky to watch both parents bring food to the nest.

The Canada Goose nest on a cliff near Belvedere Castle hatched late last week with three goslings. One egg didn’t hatch. The three got down to the pond and have been eating on the south lawn area and getting handouts from tourists.