Big Migration Movement Behind Cold Front

   It appears the cold front that brought rain and a day of falling temperatures may also be causing a big movement of birds.

    You can see the line of showers that is crossing St. Louis, Chicago and Green Bay. To the west of that line all those circles of color are birds. Backyards should be full of new stuff tomorrow!

Keep looking up.

Fall Vireos

   Vireos are a group of birds that sometimes don't get as much attention as other groups like warblers and sparrows but they deserve more admiration. In the fall identifying some species can be tricky. I've learned this the hard way. At this time of year in my area it is possible to encounter at least 4 species of vireo at the same time. Blue-headed, Philadelphia, Warbling and Red-eyed Vireos are common migrants in Minnesota.

   Last weekend we had three of those four species end up in our nets. Easily identified by the stripe pattern on it's face is the Red-eyed Vireo.

 

   It shows an "oreo cookie" pattern of a light stripe bordered by dark stripes on both top and bottom. Young birds in the fall show a brown to red-brown iris. Some individuals can retain this color into the following spring. Adults have the bright red iris that gives them their name.

   The ability to separate the Warbling Vireo from the Philadelphia Vireo can be more difficult. Both were in our hands and there are a couple of things to look for that separate the two.

    This Philadelphia Vireo shows the yellow throat that clinches it's ID. The cap on the head is gray and the line through the eye seems to me to be more bold. It is a bit smaller than the Warbling Vireo and feels that way in the hand.

   This Warbling Vireo is a bit larger and shows a white throat and chest. The crown color is more olive compared to the Philadelphia. A second characteristic for separating the two is only seen with the bird in the hand. Warbling Vireos have a relatively long tenth primary (p10) on the wing while p10 on the Philadelphia Vireo is "vestigial" or completely absent.

   On this bird you can see that p10 is longer than the primary coverts of the wing. This is a quick characteristic to check when trying to decide between Warbling Vireo and Philadelphia Vireo. Having a bird in the hand allows for a whole different approach to identification versus looking at these birds up high in a tree.

   With the weather continuing to be warm and dry this weekend should be good for getting out into the field. The Warbling Vireos should just about be gone but the Philadelphias and Red-eyed will be moving through for a while yet. The next big group will be sparrows!

A Quick Correction

Just a quick note. A couple of much smarter people than me pointed out the difference between fault bars and growth bars. The chickadee is showing growth bars in its feathers. I have updated the blog to reflect this correction.

As soon as I get the monkey trained, the errors should go down...

Feather Molt and Energy

    With all the birds we handle while we're banding, once in a while we have one that gives us insight into the daily life of a bird. The first two photos below are close ups of the wing and tail of a Black-capped Chickadee we caught Sunday while banding. The light and dark bars on these feathers are referred to as growth bars. This phenomenon has been known and written about for over a hundred years but it is not something most people see unless they have a bird in the hand. We now know that this pattern is caused by conditions that vary from day to night as the feather develops. In this case probably the alternation between day when the bird is being fed and night when it is not. There is also a situation where there is a significant interference with access to nutrition that is reflected as fault bars, an actual weakening of the feather usually in the flight and tail feathers.

       In other words, things like poor weather, a parent bird being prevented from feeding young birds regularly, or general lack of prey items can result in fault bars and sometimes even a weakening in the feather structure itself. The symmetrical pattern of the growth bars across all the feathers is different. This bird shows a pattern where one light bar and one dark bar represent 24 hours of growth. There are cases where an adult bird might lose and replace a single feather and that single feather shows growth bars but when all the tail feathers or wing feathers show this it can be an indication but is not definitive of a juvenile bird since those feathers were all being grown at the same time.

      Even normal, seasonal molt requires lots of energy and different groups of birds show different patterns of molt. Because molt is tied to energy several strategies have developed. Some migrant birds molt after they have fledged their young but before they leave the breeding grounds. Others begin their molt on the breeding grounds but suspend their molt during migration and finish the process on the wintering grounds. Some birds just wait until the reach the wintering grounds. Local birds that do not migrate have slightly less concern about energy and show a more protracted molt.

    No matter what, molting in a whole new set of feathers is a big investment. The picture above is of an adult Gray Catbird wing from Sunday that is growing new primaries as it is moving south. This individual will need to find enough energy to both grow these new feathers and to continue on its migration.
     The good news is that all those "confusing fall warblers" that are moving through right now will reappear next May with a brand new set of feathers that will make most of them easier to identify. And don't even get me started on the juvenile sparrows that are just now showing up!

Banding on a cool, cloudy morning

I had such high hopes for our banding program yesterday morning but the weather and wind did not cooperate. We weren't skunked but the numbers and species were not what they could have been. We did catch a couple of birds that are moving through right now - Swainson's Thrushes. They were both youngsters and must have just arrived as they had no stored fat on them.

This Gray Catbird was another bird I suspect was moving through because I think the local nesting catbirds have already left. This bird was molting in feathers on most of it's body. The only other species we caught were a couple of Black-capped Chickadees. Even common local species can teach us something once in a while like one of the chickadees did. Tomorrow I'll post some pictures of the chickadee and catbird and a little note on feather molt and energy.

The South is Rising Tonight

...at least the birds are. The radar at 10:00 pm CST shows really heavy movement south from the Ohio River Valley and central Missouri. Pretty much anywhere below the Mason-Dixon Line (do you see a theme in this post?)

Anyway this is what it looks like now -

Of course, up here in Minnesota where we're having a bit of a cool spell there appears to be little if any action tonight. No matter. I'm headed out to the banding site tomorrow morning and then to Ritter Farm Park on Sunday morning to see if I can add some jewelry to the warblers and vireos passing through. I'll post an update.

KEEP LOOKING UP!

A Day of Surprises

Sometimes working on a site you don't control has it's surprises. My banding site sits on the grounds of the school where I teach. One of the odd characteristics about the area here is that we have a lot of underground oil pipelines running all over the place. There is a refinery not too far away and long story short, these pipelines have right of way agreements as too their management. Well, I showed up to get ready for fall migration banding and holy #!&;*# they mowed down everything on top of the pipeline. One of my net lanes is now non-existent!

They got it down to pretty much bare soil. As upsetting as this might seem, it actually is something that happens here every few years. It gives me an opportunity to see if this changes the species that show up and it helps to concentrate some birds toward my other net lanes.

Well Sunday morning was a break in the oppressing hot, humid weather we had been experiencing for the past week and Monday looked to be hot again so I had a small window for banding.  I sat for 3 hours and caught not a single bird and the landscape was pretty quiet except for high flying Cedar Waxwings and a very vocal Cooper's Hawk down the lane. Then at 10:30 we saw some flitting along the edge of the trail and it was definitely warblers foraging in the brush. A quick check of the nets made the waiting worthwhile.

This bird was a first for me. I had never banded a Black-Throated Green Warbler before and was I excited! Fall warblers can be a challenge but this individual was very cooperative. Pretty stunning in the hand.

Then of course there are the truly difficult fall warblers. This fall plumaged Bay-breasted Warbler can give you fits when compared to a fall plumaged Blackpoll Warbler. Luckily having caught one last fall I knew what to look for and the coloration on the sides of the bird and the color of the feet clinched this one for me. Always kind of exciting when you walk up to the net and go "uh-oh".

If they were all easy it wouldn't be as much fun now would it? We had a total of 13 birds, but as is typical of migrating warblers, they were a mixed flock and we only got one of each species.

Other birds we caught with these warblers included 3 Black-capped Chickadees, 4 Red-eyed Vireos and a Downy Woodpecker.

One of my favorite warblers (if one can have a favorite from this group) is the Black and White Warbler. Not only is their coloration striking, their behavior is so not like other warblers at times.

Finally we have a Magnolia Warbler. Another great catch and looking so different from when we catch them in the spring. The white band across the entire tail is an easy ID mark. It looks like it's having a bit of a "bad hair day" because I had to look at its skull to see if it was a young bird or not.

"Skulling" is another one of those odd skills banders work on in order to get the best data they can from the birds they handle. It sounds worse than it actually is. A young birds skull, like a young human, is not fully formed when it hatches. By wetting the head feathers and looking at the skull through the thin skin on the head you can often see "edges" where the bone is still growing to form a complete skull. Some species might not finish forming their skull until well into the winter.

Things should be picking up for the next few weeks. Once the warblers push through we'll see the sparrows next. If you think fall warblers are tough you ought to see young sparrows in the fall...