Friday, August 26, 2016

Fri-D: How Old is that Shorebird?

[Click to enlarge photos.]

Adult shorebirds have been heading south since late June or early July, and now the juveniles - young of the year - are pouring through. There are plenty of adults still around, which leads to confusion, especially when using colors and patterns to identify the birds. How, for example, can the two birds above be the same species?

Well, they are, Least Sandpipers to be exact, which could have been told just by the yellow leg color and small size (unless you're trying for an exotic). Juvenile shorebirds, heading south with their first set of feathers, are usually well patterned and often quite bright. In many species, the patterning is formed in part by broad buff, white or orange edges to the upperpart feathers, created a scalloped efffect. On juveniles, the feathers are all the same age and in uniform, good condition. Thus we can say confidently that the left bird above is a juvenile. 

A word of caution: juveniles of a given species can be variable one to the other. In particular, some are brighter than others, often because the bright ones have just come down from the nesting grounds and the feathers haven't had much time to show wear. We see lots of birders trying to create something exotic out of juvenile shorebirds because of this variability - there are bright and dull Semipalmated Sandpipers, Least Sandpipers, etc., so it is important to develop a feel for this variability.

The right bird above is an adult. Its feathers are not all the same age. The wing feathers are about a year old, while the body feathers were molted in last late winter and spring as the bird assumed breeding plumage. It is now in worn breeding plumage. The wing "panel" - the coverts - contrasts with the rest of the feathers because it is worn and uniform gray, compare it to the same place on the juvenile. I'm not seeing new, gray winter feathers coming in on this bird's body, so it is wearing worn breeding feathers. Since it is late August, this suggests this particular individual will winter in South America, and will molt when it gets there. If it were going to winter farther north, it would already be molting.

Another pair, this time Lesser Yellowlegs, adult on the left and juvenile on the right. The adult is in worn breeding plumage and does show new, winter-plumage gray feathers coming in on the back. The juvenile is neatly patterned with white spots on the edge of the upperpart feathers.

Both photos are from the South Cape May Meadows, NJ, the Least Sandpipers this week, the yellowlegs a couple weeks ago.

Monday, August 22, 2016


Flight? Not. As in not this morning, Monday August 22, 2016. Front passed too late, stormy to our north, blah blah blah - and no warblers. So tomorrow? Other than that the winds are going to swing to the NE, which is less good, yes.

Yet another predictor of big flights is simply, whatcha got in the pipe? Meaning, if you've had two weeks of lousy migration weather (and we in Cape May have), then the pipe is full of birds ready to come. Hopefully.

Sunday, August 21, 2016

Flight? Flight.

[Graphical weather forecast from Sunday, August 21 2016 at about 9:15 a.m., courtesy of NOAA. Click to enlarge.]

An additional very useful tool in the hocus pocus of predicting bird migration is the National Weather Service's graphical forecast, like the one above. I mainly look at the second row, which shows forecast wind direction and velocity. In fall, what I want to know three things:

1. When is the wind going to come around to northwest (as it invariably does at least for a little while when a cold front crosses the cape)? Above we can see that sometime in the middle of the night Sunday that will happen. This is good, but it would be better earlier. However, we also need to consider conditions well to the north, up to several hundred miles, because that is our "sending zone:" the place our Monday birds will be coming from. It looks like the front will only clear the western part of New York and New England in time for birds from those areas to migrate Sunday night, which is a bit of a bummer.

2. When the wind does shift, what will it's speed be? I like to see speeds in the teens - strong enough to drift birds to the coast (and therefore also cause them to engage in re-directed morning flight). Wind in the 20's or higher can be too strong for some migrant landbirds.

3. How much of a west component will the wind have and how long will it last? It looks like beginning around midnight Sunday night, there will be plenty of west component until the middle of Monday night, when the little flags on the graph start leaning to the right - i.e. east. This is also a bummer, because it means Tuesday will be less good than it would have been if the winds had stayed west.

The forecast above is actually about perfect for a hawk flight, except for one thing: the date. There will be hawks in Cape May on Monday - Ospreys, harriers, an eagle or three - but not the piles of hawks there would be if this was a forecast for mid-September or later.

The upshot for Monday: definitely a flight of landbirds, but perhaps not as many as if the front were to fully clear the northeast early in the night. Then hawks. A good day.

Thursday, August 11, 2016

Thoughtful Thursday: Children

[I watched and admired as this Common Tern parent, right,  flew past its offspring as the mewing baby begged on the beach. No fish until you fly, kid. 10 passes later the kid made a short, weak, but brave flight, and was rewarded on landing with an Atlantic Silverside, a very common baitfish in our waters right now, called spearing by fishermen. Stone Harbor Point this morning, click to enlarge.]

“We cannot always build the future for our youth, but we can build our youth for the future.” 
― Franklin D. Roosevelt

Monday, August 8, 2016

Hocus Pocus

Sometimes the Hocus Pocus migration prediction magic actually works.

[Northern Waterthrush in morning flight at Higbee Beach WMA, NJ Sunday morning.

Only, it's not magic at all, in fact it is relatively simple stuff to know when a good day is coming (predicting truly massive flights is less easy, but still sometimes possible.) You look at the date - early August, OK, what species are likely migrants now? (see blog below.) You look at the weather map and charts - when is a cold front going to pass through Cape May? Will the winds turn to northwest before nightfall or at least sometime in the night? Plan to go birding the morning after. And, if you want, check the weather radar before you go out to gauge the extent of migration.

[Velocity weather radar at 2:40 a.m. Sunday morning, August 8, 2016, from Dover, DE. Blue colors are birds flying towards the station, hot colors are birds flying away. Notice they avoid flying over the water; this radar image with a "bite" out of it on the east side is a great predictor for birds on the coast in fall. The blob at the bottom right is a rain squall associated with the cold front that passed.]

[A bit of a surprise, this male Tennessee Warbler on Sunday morning was among the earliest southbound Tennessee's ever recorded at Cape May, right in front of the concrete platform in the first field.]

As of now, the next little hit of migrants seems likely Tuesday-ish next week, but that's 8 days away, so don't hold me to it. Dribs and drabs until then. Yesterday morning I ran into about 40 individual warblers of 8 species, and heard of at least two other warbler species seen by others. Not to mention a couple dozen Eastern Kingbirds, Orchard Orioles, waxwings, etc. And the fall mosquito crop seemed not to be abroad yet, though there are still deerflies around. . .