Monday, September 17, 2007

a bird in the hand…

Last Monday (Sep 10) WREN staff and volunteers were invited to watch bird banding a Dave’s place. Even though the species found there are not necessarily wetland species, it was a great learning experience. When we arrived just before 8am, Dave was not there but the banding equipment was all laid out on the table.

When he arrived with the box of birds we gathered round to see who had been caught in the mist nets. Dave has 11 nets set up on his property. The two things folks always want to know about bird banding are: 1) Does it hurt them? and 2) Why do it? We will get to that later, Dave tells us. Right now we have birds to band!
Data such as the date, time, and location are always recorded for each bird captured. Dave tells us that the age and sex can be difficult to determine at this time of year. The first species was a little unusual – Hammond’s flycatchers are not common in the greater Eugene area. This is a migrant heading south.

The other flycatchers that Hammond’s might be confused with are the Willow and the Pacific Slope – both of which have a larger bill. The lower mandible of the Hammond’s bill is two toned: yellow fading to black – the Willow and Pacific Slope have solid yellow lower mandibles. Now this kind of detail may be difficult to notice in the field but when the bird is in the hand – it is very clear! Another detail is the eye ring. The Willow doesn’t have one, Pacific Slope’s is whitish yellow and the Hammond’s is white/dingy white. That also may be difficult to see in the field!

This is a young bird – born this year. We know this because the wingbars are buffy – not white. Now heading to Central America, this bird may have been born in the Cascades.

Next up we have a re-captured Black-capped chickadee. Dave tells us that he is always concerned that he might hurt a bird, but he is a little less so with a chickadee – the are pretty tough little guys with thick legs and feet for all their acrobatics foraging in the trees – often hanging upside-down. It is nipping at Dave’s finger when he takes it out of the bag. He shows us the color bands it is wearing… on the right leg is a metal over purple, on the left a light green. No other bird will get that combination. We would not confuse this with a mountain chickadee because they have a different facial pattern – even though both species have dusky backs. This young one was most likely hatched in April and still has some of the feathers it came out of the nest with.

The next bird is also a re-capture – this one is a Chestnut-backed chickadee. This one is an adult – this time it can be aged by the fact that it has been banded before! We can look at its chestnut back.

When the next bird was removed from the net it was screaming, but when Dave removed the Downey Woodpecker from the bag to show us it was quiet. Birds may vocalize in reaction to being handled – not necessarily because they are in pain. When we look in the field guides we notice right away that this is an adult male. Juveniles have red in the front of the head. When they mature, the females lose the red, the males transfer the red to the back of the head.

Then we focus our attention on the tail. The feathers divide evenly into two sections. Woodpeckers have strong tails to balance while feeding on the trees. Dave points out that the shafts of the tail are very stiff – if not they would wear out fast! But these shafts do not go all the way to the tip of the feathers as they might in another woodpecker, a Hairy say, which does a lot more probing in tree trunks. Downeys will also feed on branches. Dave shows us that the outer primary feather is growing in on both wings.

The next bird also screamed when removed form the net. It is a young female Spotted towhee that has be re-captured. Dave tells us that the dull eye and the dull plumage with lots of brown let him know it is young. If it was a male there would have been more orange and red in the eye. When it molts next time it will be darker. This ground feeder has well developed legs and long nails for scratching.

Before we go out to check the nets, Dave tells us that since it is supposed to get into the 90s today (which is hard to believe as we shiver around the table!) that the activity will drop off fast as it warms up. He will probably roll up the nets and close up shop around noon. It is too dangerous to have birds captured during a hot afternoon because they may overheat. Checking the nets is called a “net run” – we move fast so that we don’t scare the birds away from the nets. The group leaves at 8:35 and returns at 9:00am.

Dave removes one of many Swainson’s thrushes (SWTH) from a bag. This one is squawks a bit. Dave examines it, “see this mark?” (a tiny light spot on the feather) that means that it is a juvenile. It has obviously been eating blackberries! Dave begins to show us the shape of the wing and it squawks again. It begins to close its eyes too and Dave decides to let this one go. He can show us the wing on another bird. The place is loaded with thrushes right now, and he is surprised that we didn’t get one in the first batch.

The next Swainson’s thrush has no tiny light spots on it so there is a different technique to determining the age. Dave measures the distance between the tip of the tapered outer primary to the tip of the longest covert. This is a hatching year bird. The wing has projection – meaning that the primaries are much longer than the secondaries - this results in a powerful wing. Since these birds are long distance migrants this design is critical. We also learn that they may not begin to molt until they have begun to head south or even after reaching their wintering grounds.

The next bird has been munching blackberries too. This one is a Song sparrow though. Dave can tell it is a young one – based on its overall plumage: the streaks on the chest are not well defined, fleshy bits at the base of the bill, and the feathers are lax and loose. We ask Dave when it might have hatched. Since Song sparrows can have 2 or 3 successful broods during a breeding season, and this one’s feathers are not showing much wear, Dave guesses about 5 or 6 weeks ago. He shows us the short distance between the primaries and secondaires resulting in a short round wing – perfect for a bird that does not travel far.

When Dave first moved to this property, a retired biologist living down the road discovered a Pine Siskin that Dave had banded. After trapping the bird at his bird feeder, the neighbor called in the band number excitedly, eager to learn where this bird was banded. Dave called him back to let him know that it was captured about half a mile away! Now that Dave had been here for about 14 years and knows his neighbors, some of them are willing to let him band on their property. It would be interesting to find out, for instance, how far some of the young resident birds disperse.

The next bird out of the box was another Swainson’s thrush. We note some abrasion on its wing – I wonder if it was those blackberry thorns. There are no light marks so Dave again measures the distance between the tip of the tapered outer primary to the tip of the longest covert – it falls right in between the age categories!

After another Swainson’s thrush, Dave tells us he has saved the best for last, and says he might have to strap me in! Ooooh! What could it be? A really sharp dresser that’s what -- a male Red-breasted nuthatch! Dave tells us that they are early nesters so the molt is over by now. The black on the head is jet black and the grey on the back is slate colored. Wow! Dave shows us the foot – designed for foraging on tree trunks. We can see it breathing and we ask about the heart rate – it is a rapid trill. Dave puts the bird close to his ear to listen. When he pulled it away there was a small fluffy grey feather stuck to his cheek.

One morning recently Dave was out on his property. It was in the 7 o’clock hour and he heard erratic wing beats coming into the trees, then the whistled note of a Swainson’s thrush. Since most migrants travel at night, Dave suspected these birds were taking a rest. He mentions to us that warblers (among other songbirds) cross the Gulf of Mexico non-stop.

It is now 9:38 – time for another net run! This time I go with. Today there have not been signs of a mixed flock, one with warblers for instance. As far as thrushes go, the Hermit’s will arrive soon, as the Swainson’s are leaving, later the Varied thrushes will arrive. Soon there will be a big change in the species composition.
At the second net we find a Swainson’s thrush. After passing some more nets, Dave stops and I notice the brightest yellow small bird! I was so excited I grabbed Liz’s arm – strap me in! It was a WIWA – more on that later.

We hear a Douglas squirrel, but overall things are pretty quiet. In another net we find another SWTH. This one evidently hit the net hard, for it is tangled. Dave notes that it is heavy. It has put on weight for its journey!

We hear and see a chickadee and head to the “thrush net” – a net set in a narrow thick area. It is empty. Then we pish a flycatcher and see a towhee. We head to the “ultimate thrush net” (even thicker and darker surroundings) and find one waiting for Dave to take it out. Dave surmises that he gets about 3/4ths of his thrushes here.

Back at the gazebo at 10:03. Not bad. First we look at that heavy SWTH. Dave says it weighs twice as much as the others. There is a spot, a long taper on the first primary, and the distance is 3mm. All this leads to the conclusion that this is a hatching year bird. Dave tells us that there is a depression in the center of the wishbone. Right now that area on this bird is filled with fat and Dave can feel it! He blows the feathers to show us that the area is white – if it were muscle it would be red. Wow! Good luck on your way south, junior!

The next young SWTH leads Dave to mention that these migrants are probably coming down at the appropriate time – usually in the dark. Then they start foraging if conditions are good, or move on if not. Birds also queue in on other birds by vocalizations. A good area will have lots of birds. Because Dave’s property has so many blackberries there is a lot to forage.

After looking at the other SWTH, Dave brings out the showstopper. A “wee-wa” aka Wilson’s Warbler. We look at the amount of green in the top of the head. Dave consults the text. He knows that it is not a male, but either a young or adult female. It has an enormous eye, for it prefers -- and is designed -- for dense cover. We then get into a discussion on molting. It is confusing – the “rules” seem to be broken more than they are followed for many species!

Now that we are done looking at the birds, Dave spends some time talking to us about the reasons to band birds. Many people think that banding birds is to see what far-off region they travel to. While this is true, there is the perhaps less glamorous reason of establishing baseline data for an area. On Dave’s property he is trying to determine such things as what species are there, what percentages are adults, what percent are female, and where to the young go. The year-round residents may get colored bands on their legs. This will allow Dave to ID individuals (no two birds get the same color combo) with his binoculars. Others, such as all those Swainson’s thrushes, do not get color bands – they will probably never be here again.

Many thanks to Dave for a wonderful morning!

1 comment:

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