Monday, August 2, 2010

Some Recent Ramblings...

Fall migration has certainly started, but things are still quiet enough at the moment that there's time to spend a bit longer actually watching birds instead of just looking at them. Bunker Pond has certainly been a great place to hang out of late, with the birdshow seemingly changing by the minute - turn away for a moment and you'll miss something!

Water levels on Bunker Pond are unusually low at the moment, perhaps surprising after the very wet spring we had, but the hot summer has certainly taken its toll. As fish become concentrated in the ever-shrinking pools,  fish-eaters arrive by the score. Recently I counted 58 Great Egrets on Bunker Pond, as well as a whole host of other stuff. [Photo by Mike Crewe]

Take a stroll along the south side of the pond on the dirt trail and you'll soon reach the little wooden service jetty. Closed to the public, this is a great place for birds to gather and is particularly favored by Forster's Terns. It's well worth spending some time getting to know this species here, as it is usually amongst a flock of Forster's that you may well find yourself looking for a Roseate Tern some day. In late summer, most North American birds are well into their post-breeding molt. The downside of a molting bird is that it can sometimes be harder to identify; the upside, is that you can learn so much more about birds in general (of course, you can just enjoy looking at them too!).

Forster's Terns at the Bunker Pond jetty. The second and third birds back from the front are typical of adults in late July/early August, with legs still mostly bright orange (though a little darkened), bill starting to darken and the black crown feathers being replaced with white, starting on the forehead and working back. But look more carefully and you'll see a whole array of variation in molt timing among these birds - why is that? Well, it could be related to diet (a bird on a poorer diet may molt more slowly if it isn't as 'fit') or it could be that birds who finished breeding earlier (maybe the eggs or young were predated) start to molt earlier. Notice how the front bird is further into its head molt and its legs are darker than the next two. But look also at the fourth bird. This bird is so far into non-breeding plumage that it may well be that it never actually acquired a full adult breeding plumage, something that typically happens to second calendar-year birds. They all look different, but they all tick all the boxes in the Forster's Tern ID suite. [Photo by Mike Crewe]

Often, the least familiar plumages are those worn by juvenile birds, because the plumage is around for such a relatively short length of time. Young birds grow real fast and need to get out of the nest and flying to be safer from predators. One of the strategies that many birds use to help achieve this is to have a set of feathers that are low grade and not intended to be around for long. The juvenal plumage gets the bird through a difficult first few weeks for many species and is soon molted out to be replaced by longer-lasting feathers which grow more slowly and are stronger.

Unless you live relatively close to a Laughing Gull breeding colony, you may rarely see one in juvenile plumage as they molt into their first-winter plumage a mere three or four weeks after leaving the nest. This little guy was in the state park parking lot and, having recently ridden out a shower of rain, his feathers are already looking a little frayed at the edges. [Photo by Mike Crewe]

Molting can be a stressful time for birds; it probably takes up a lot of their energy reserves which will weaken them for a while and many will find flight less easy when there are gaps in their wings to break up the airflow in flight. It is certainly noticeable how many songbirds become much harder to find during their molt period in late July and through August. On a recent Wednesday morning walk, I was asked where had all the male Mallards gone as their was not a green head to be seen. Well they are not hiding with the passerines, they are right in front of you, but you might not notice them. Many male ducks have a summer molt which puts them into what is often called an eclipse plumage; this plumage is usually very close to that of the female, rendering them less obvious to predators at a time when they are most vulnerable to attack.

Male Mallard in eclipse plumage at Lighthouse Pond. The trick to telling males from females in this plumage is the bill. Females have a brown and orange bill at all times, while eclipse males have a slightly greener version of their otherwise yellowish bill. [Photo by Mike Crewe]

Don Freiday's post back last Sunday on Fish Crows gave us a nice insight into their molt strategy and I thought I would just add this picture which nicely shows a bird mid-molt (click to enlarge). Notice how the wing molt is not random; the feathers are molted sequentially, with both the primaries and secondaries starting from the middle of the wing and molting away from each other (thus outwards for primaries, inwards for secondaries). It's easy to tell the glossy, blue-black new feathers with their crisp edges from the frayed old feathers which have faded and become quite brown in the sun. There is slight confusion in this pattern on the innermost part of the wing as the bird has already molted some of its tertials which look nice and shiny and new. [Photo by Mike Crewe]

So here's a challenge for budding photographers! Don's post set me thinking, as he mentioned that the Fish Crows were eating cicadas along the back of the beach by the Plover Ponds - and indeed they are. However, there are no trees here and cicadas generally live in trees, so where are they getting the cicadas from? Well, above is a picture of a large wasp called a Cicada-killer which is a common species around parts of Cape May and loose colonies make their nests in burrows in the more stable parts of sand dunes. They catch and paralize cicadas (in flight - awesome!!) and use them as food for their young. So it occurs to me that the Fish Crows are probably robbing the wasps of their hard-earned kills, but are they stealing them directly from the wasps (and thus risking injury) or are they digging them out of the burrows when the wasps are away? It's your chance to be the first to find out - and send me a photo of the event! [Photo by Mike Crewe]

On a different note, don't forget to keep an eye on the sky when you're down at the point - this Whimbrel passed right over my head and joined a second bird down on the Plover Ponds a few days ago during a lunchtime stroll. [Photo by Mike Crewe]

And finally.....
Was it really that long ago? A bunch of us headed out to the crab shack by the Bree-Zee Lee Marina recently to celebrate the 6-month anniversary of the Ivory Gull at this very venue. Don't remember being in short sleeves there last November though, especially that hideously windy day when Jim Dowdell first uttered those immortal words... Now let's see - crabs, french fries, beer, optics, wife, friends - yep, looks like a good night!! [Photo by Mike Crewe]

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