Käyttäjän mikaelb päiväkirja

(Above is a beautiful public domain photo of a Blue Jay vocalizing that I found on Flickr. Click on it to go to the photographer's photo stream.)

I've been interested in a body of knowledge call "Bird Language" ever since Jon Young wrote the book "What the Robin Knows" in 2013. It describes and organizes patterns of bird behavior and sounds around perceived danger that he calls "alarms." If you can recognize when birds are exhibiting alarm behavior, you can sometimes determine what the source of that alarm is. I've found snakes in trees by first recognizing songbirds alarming around a particular area in the canopy. And I've gotten to see a few more Cooper's Hawks and Sharp-shinned Hawks over the years by recognizing other birds' alarms that the hawks trigger.

Blue Jays have always been difficult to interpret in this context. Sometimes you see them mobbing a hawk while making their "jeer" calls. But it seems like just as often, maybe even more often, they get together and jeer and jeer and jeer for no apparent reason.

But recently I made a discovery about Blue Jay alarms. Back in November one morning on Lake Creek Trail, I heard a nearby Blue Jay making jeer calls. And then I heard a low croak from the same direction. I found the Blue Jay and saw it make a few more croaks as it concentrated on a small area of low dense brush. Looking into this brush I was excited to see a roosting Eastern Screech-Owl!

Since then, I've been listening for these croaks from Blue Jays. And when I hear them, I can usually find both the Blue Jay and a hawk that it's harassing. The croaks seem to be a pretty reliable indicator that a Blue Jay is actively confronting some kind of predator. Much more reliable then the jeers.

A couple days ago I was able to record one of these croaks. A Broad-winged Hawk was perched in my neighbor's backyard and a Blue Jay flew in to harass it. I started recording audio on my phone hoping to record a croak, and I did! See the attached audio observation of Blue Jay. The audio clip starts out with some jeer calls, and then at about 10 seconds there is one croak. The Blue Jay made this croak as it dove at the hawk. It's the last Blue Jay sound on the clip.

I also attached the Eastern Screech-Owl observation from November when I first noticed this croak and wondered what it was.

On Sunday morning Joanna Rabiger and I met with HCC staff member Sarah Dean on Hill Country Conservancy's Nalle Bunny Run wildlife preserve to create another virtual tour. I'll update this post with a link to the video when it is available.

A highlight of the morning was a brief sighting of a silent Golden-cheeked Warbler that Joanna spotted at the beginning of the trail to the spring, at the edge of oak-juniper habitat. I was unable to photograph this bird but it was exciting to see. We don't get many observations of this species on the preserve, even though the preserve is managed for Golden-cheeked Warbler habitat. We think the habitat is a bit too small and isolated to attract a breeding pair. This might have been a post-breeding wandering bird, or even a bird already on its way south.

Attached are some other observations.

Here are the same photos on Flickr:
https://www.flickr.com/photos/mikael_behrens/albums/72157714828598021

And here is our complete bird list on eBird:
https://ebird.org/checklist/S70733951

Update 6/30/2020. Here's the video: