Last day of spring 2019 banding!

Today was our last day of spring banding. Once all the data has been processed I will post the season's totals. What species do you think we captured the most?

Though today was a little slower than the last couple of days, the diversity of species was interesting. We heard several Townsend and Wilson's Warblers, but didn't catch any. We did capture several woodpeckers and enjoyed the opportunity to compare them in the hand. Here's footage from a gorgeous female Downy Woodpecker we caught:

05/14/2019: Wilson's Warblers have arrived!

 We had a beautiful first of season today. We captured two gorgeous Wilson's Warblers! Both were male (males have a black cap) and easily became the "cool bird of the day".

FIVE first-of-seasons!

We had a great day at CFMS. We captured a total of 20 birds of eight different species. Five of those species were new for the year!! We captured a Hairy Woodpecker, Hammond's Flycatchers, American Robins, Yellow-rumped Warblers (Myrtle), Dark-eyed Junco (slate colored), Savannah Sparrow, White-crowned Sparrow, and Common Redpolls.

Three of our recaptured (two Yellow-rumped Warblers and a Hammond's Flycatcher) were captured and banded as adults last spring; each of these birds are now at least two years old but could be older. The Hairy Woodpecker we recaptured was a male that we originally banded back in the spring of 2017 as a 'three-year-old'. He is now at least five years old! We also suspect that he has a nest near our station! 

First-of-season: Hammond's Flycatcher

We captured our first Hammond's Flycatcher of 2019! Flycatchers are often tough to identify to species; in my opinion, they're one of the few groups that are easier to identify in the field while birding rather than in-the-hand. Vocalizations are key to identifying the species of the bird. In-the-hand, the bird is quiet and we rely on a series of measurements and calculations to determine the species. For starters, we examine feather shape of certain feathers, the relative length of primary feathers, tail length, wing length, bill width and length. Sometimes this isn't enough. If we are unable to identify the species we must release the bird without a band.

Returning Dark-eyed Junco

Today was our warmest day at the station; we didn't need the heater at all! Our thermometer read 65.6F when we closed the nets for the day. Despite the glorious weather, capture rates remained low. We only captured three birds today (two Common Redpolls and one Dark-eyed Junco). However, we did have the opportunity to observe two different birds escaping from our nets. This is likely a common occurrence, but something we don't often see. 

We were lucky to have the good fortune to share one of our captures with a school field trip today. Tait, a banding apprentice, shared a Dark-eyed Junco that was originally banded in the spring of 2018 (May 11th). It's only been a few days shy of a year since we last saw him! Last year we were unable to determine whether he was male or female; this year we solved the mystery!

Dark-eyed Juncos

After being 'skunked' yesterday, it was nice to have a quick start to our day with two Dark-eyed Junco captures. A gentle drizzle started around 9am and was 'off-and-on' all morning. We finished off our day with a total of three captures.

Our first spring migrant!

Dark-eyed Junco (slate colored)

We kicked our morning off with a great start. We saw Fairbank's first Hammond's Flycatcher of the year! It was quickly followed by detections of Yellow-rumped Warblers, American Pipit, Ruby-crowned Kinglets, and a Wilson's Snipe!

Though we did not catch any of those species, we had a good morning and captured seven birds total. Most were recaptures (six) from this and previous seasons. Black-capped Chickadees were our most frequent species captured (three), and a Slate-colored Dark-eyed Junco was our first migrant captured of the season! It was a quick favorite for today.

Our third spring snow storm!

The predicted storm settled in late yesterday afternoon. Rain turned into snow, and many places around town had accumulation up to 2inches. The cooler temperatures, wind, and mixed precipitation did not abate until late morning. Because of these conditions, we canceled banding and closed the station for today. We hope to get back out on Monday.

Redpolls, redpolls, redpolls.

The station continues to be inundated with Common Redpolls. All of our captures were Common Redpolls; one of these captures made it's way into our nets a total of three times today! When we recapture a bird in the same day, we release the bird immediately.

Esophageal diverticula in Common Redpolls

food visible in the 'E.D.'

The days of great weather have continued. Our capture rate improved today with the capture of three Common Redpolls; each of the three individuals varied in the volume and type of food stored in their esophageal diverticula. 

Esopha-what?! 

Esophageal diverticula are small pouches attached to the esophagus (the tube that runs from your throat to your stomach). This is not necessarily the same thing as what is commonly called a 'crop'; in other words, all crops are esophageal diverticula, but not all esophageal diverticula are crops (for example, many grouse species have esophageal pouches that they inflate as part of courtship display). There are three categories of esophageal diverticula: 1) 'real crops' are well developed, round and bilobed , 2) 'false crops' are typically long, narrow and small in size, and 3) 'rudimentary crops' are small and simple (i.e., they lack complex function or much supporting anatomy). 

 A small number of birds (mainly birds in the finch family that occur at Northern latitudes) have esophageal diverticula that are used as simple storage pouches and is a 'false crop'. This simple pouch's primary purpose is to temporarily store food for acute and energetically demanding events when food is not available. For example, consider how energetically demanding it is to maintain your body temperature outside in the middle of an Interior Alaska winter. Esophageal diverticula are an elegant solution to a complex problem for residents like redpolls. They are able to forage and fill their esophageal diverticula during the short days, and then continue to eat all night long. (Perhaps, like eating a midnight snack without leaving your bed?) These extra calories that can be consumed during periods when they can't forage allow them to survive conditions that would cause most birds to perish. Brooks (1968) suggested that this single adaptation extends the survivable temperature extreme from -30C to -68C. Pretty rad, huh?

At CFMS, we monitor how "full" the esophageal diverticula of redpolls are. Sometimes we are even able to determine what the bird has stored in the pouch, because their skin is translucent and the tissue between the pouch and skin is very thin (check out our picture from today). If larvae have been eaten recently we can even see them moving!