Saturday, August 19, 2017

The enigma of species missing south of Lake Pontchartrain

Yesterday, Fox 8 posted this video of a beautiful male American Kestrel on one of their cams:

Apart from being a real looker, this bird is also of interest because it is here at a curiously early date-  the species nests on the North Shore, but is normally absent on the South Shore in the nesting season.  Being here before the normal fall migration period suggests it may have wandered down here after it finished breeding.  Such post-breeding dispersal in late summer is pretty widespread in North American birds.

But back up a bit.  Why would Kestrels nest on the north side of Lake Pontchartrain, but not the south side?  Isn't there plenty of acceptable habitat down here?  There does appear to be.  However, fully seventeen other species of North Shore nesters are also absent down here despite apparently suitable habitat:
Wild Turkey
Swallow-tailed Kite
Broad-winged Hawk
Red-tailed Hawk
Belted Kingfisher
Red-headed Woodpecker
Yellow-throated Vireo
Eastern Wood-Pewee
Wood Thrush
Swainson's Warbler
Kentucky Warbler
American Redstart
Yellow-breasted Chat
Summer Tanager
Eastern Towhee
Blue Grosbeak
This used to be true of Eastern Bluebird and Northern Rough-winged Swallow as well, but they have become more regular nesters on the South Shore in recent years (or so it seems to me).  In reverse, the Bobwhite and Kentucky Warbler were more regular as nesters on the south side decades ago than they are today.

Why aren't all these species on the South Shore?  I and others have pondered this for many years, without a really plausible explanation yet emerging.  A biogeographical mystery under our noses!


Sunday, July 23, 2017

Fall migration milestone: first Yellow Warbler reported

Although some migratory shorebirds are usually reported back weeks earlier (see my late June post), to me one of the pivotal moments of each fall migration is the first report of a Yellow Warbler.

One was reported in St. Tammany yesterday, by Jane Patterson in her back yard.

I normally expect to hear of a Yellow somewhere in the state at the very tail end of  July, but this one was a few days earlier than I anticipated.   It is the onset of a larger movement-Yellow Warbler normally seems to me the most numerous August migrant in the New Orleans area.  Because it is also one of our migrant species with the greatest propensity for "morning flight" (active migration in the early AM), it is not unusual to hear one giving its seet note overhead on any morning during the month.  I have spent many hours listening for these birds in many locations on August mornings, and have on occasion observed movements of up to 100/hour both on the lakefront and in Old Jefferson.  Most such birds appear to be westbound, and presumably are bound to circumnavigate the Gulf.  They do also stage larger corrective flights at South Point on August mornings with northeast winds, but such winds are hard to come by so early in the season, since we are generally still out of range of the cool fronts that create them.  I have long tried to figure out when during August the peak of Yellow Warbler numbers occurs; my best guess is that it is in the last few days of the month, but because substantial flights can occur earlier, I am still wondering.

Friday, June 30, 2017

First fall migrants have returned!

What?  Fall migrants?

Yes, three Lesser Yellowlegs have been reported together in the northwestern corner of the state, fresh down from their nesting grounds in Canada.

Although it seems crazy, since we are barely past the solstice and into "summer," this is actually a pretty typical time for our first fall migrants to show up.   And it is quite typically a shorebird species that leads the pack.

What happens now?  Purple Martins are at peak numbers right about now in their pre-departure roosts (including under the Causeway bridge), and will be among the first breeders to disappear.  However, things get started slowly- some martins will be around until the end of August, about the same time our Mississippi Kites vanish.  At that point fall migration as a whole will just be getting up steam.  The waves of Neotropical migrants (i.e., species that winter in the tropics in our hemisphere) will build in size  through September.  Around mid-October, movements will become dominated by species that winter in our area.   Finally, major flights will end at the close of November, with just a small variety of species with atypical migratory patterns actively migrating afterwards, such as Yellow-rumped Warblers and Cedar Waxwings. 

Changes are on the way!


Monday, June 26, 2017

Brown Booby on the Causeway Bridge

Today as I was driving southbound on the Causeway at 7:25 PM, I was treated to a Brown Booby at mile marker 16.3.  It was just off the bridge, and turned in such a way as to approach the side just as we passed.

This is the exact spot where a roost of this species has been located for the last few years.  Birders crossing the bridge had been seeing small numbers occasionally, but it wasn't until a boat trip in June 2015 that allowed better viewing of the bridge structure that we discovered that there were many more there than suspected.  The peak count I know of was of 37 on one boat visit last October.   To my knowledge, there have not been any recent boat trips- a similarly large number could still be roosting on the bridge there every day.

How crazy- this species was an extreme rarity in Louisiana waters up until a few years ago.  Then they inexplicably started appearing with greater frequency- including on near-coastal lakes and even once flying with geese over the rice country!  This tropical species has been turning up in other parts of the country- and even Canada- with increased frequency at the same time as this has been happening in our own state.  These odd appearances out of range and out of habitat together pose one of the most fascinating and enigmatic ornithological mysteries I have ever heard of, and I have yet to hear an explanation that is even remotely convincing.

So the next time you cross the Causeway, keep alert!  These birds can turn up anywhere along it, but are most likely to be seen near mile marker 16.3 on the west side.  When roosting, they are invisible from the roadway- thousands of cars pass these rare birds every day, completely unaware of their presence!

Good birding, Peter

Friday, May 5, 2017

Hundreds of Mississippi Kites migrating through South Point!

This morning I took a walk out to South Point, which is the point of land from which the railroad bridge leaves New Orleans East and heads across Lake Pontchartrain to Slidell.  This is the railroad bridge visible to your left as you cross the twinspan.

South Point is interesting because it is the logical jumping off point for birds that are wanting to cross from the south shore of the lake to the north shore- by sticking northward from the southern shore, it cuts that overwater distance to 5 miles.

I had hoped for a migratory movement of some sort to be going on, but was unsure what to expect. We know big migratory movements  happen here in fall, but know virtually nothing about spring.

The point is only accessible via a mile or so walk, which starts at the "fishing bridge", which you may have noticed on the lake side of I-10 more or less across from the Irish Bayou castle.

As I walked out, I noticed  a flock of 21 Mississippi Kites negotiating the wind, which was howling from the west-northwest.   Lakefront Airport says 23 mph, gusting to 32  Felt stronger than that to me!

They made their way up to the point at about the same pace as I was walking, and we arrived there at 845 AM.

Then another flock of 22 approached, along the same tack as the others.  They headed out over the water toward Slidell and gained altitude until they were beyond range of my unaided eye.  

Around 930 the sky to the south suddenly became filled with kites- 185 in one flock!  This was far more Mississippi Kites than I had ever seen at one time before.  They were mostly low, dipping and tilting in the stiff wind.  They eventually headed out across the water, gaining height like the previous flock of 22.  I watched them through binoculars beyond naked eye visibility.

Another 10 minutes passed, and another flock- 155- appeared to the south and again headed toward me.  Shortly thereafter, another flock of 85 doing the same.

That's 468 Mississippi Kites in an hour.  That's crazy- quite likely a new record high count for the state of Louisiana, and something I never would have anticipated.

Two brief snippet videos are below, of parts of the flocks, taken by cellphone.

Good birding!




Thursday, April 27, 2017

Birding opportunity at City Park- tomorrow!

Spring is a time of boom and bust migration here in New Orleans.  According to reports, there is a little "boom" happening today in the Couturie Forest on Harrison Avenue in City Park- the city's premier migrant trap.  James Beck reported today that he and a handful of companions found 15 warbler species, accompanied by numbers of other passage migrant species, including 20+ each of Red-eyed Vireo, Great Crested Flycatcher, Scarlet and Summer Tanagers, Rose-breasted Grosbeak, and Indigo Bunting.  Warblers were let by 15 Bay-breasted, 12 Tennessee, and 3 of the hard-to-find Cerulean and one harder-to-find "Brewster'" Warbler (Golden-winged x Blue-winged hybrid).

Because winds are still from the northerly half of the compass, chances are that many or most of these birds will hang tight and still be there tomorrow- continuing migration would require departure into a head wind.  All these species migrate at night.  If you go, focus on both the live oaks and whatever fruiting mulberries you can find in more open sunlit areas.

This fallout is a puzzling.  At first glance it appears sensible- we know cold fronts precipitate fallouts by inducing birds to stopover instead of passing over us, and one came through last night.  However, this front was still hours away when the birds would have arrived across the Gulf yesterday.  This arrival is typically around mid afternoon, and the front didn't reach us until around 3 AM- about 12 hours too late to hit the birds with a headwind and induce them to ground.  There was no rain ahead of the front, so that couldn't have caused them to stop.  Could it have intercepted last night's flight instead?  No- James reported the fallout as already underway at 930 am, before birds from last night's flight across the Gulf should have reached us.

Just when you think you have migration figured out!  Sheesh.


Monday, April 24, 2017

Black-bellied Whistling-Ducks mobbing Mississippi Kite!

This morning I stepped out my front door to see seven large birds wheeling above the trees across the street.  It was a Mississippi Kite pursued by six Black-bellied Whistling-Ducks that were equal it in size (and I am sure quite a bit heavier).  

I have seldom seen a Mississippi Kite mobbed by anything- there is little reason to, since they eat insects and have unimpressive talons.  Mobbing is usually engaged by birds against larger species that pose a predatory threat.  But these six whistlers were on its case in a major way,  tracing its circles and keeping on its tail.  

I pulled out my phone to take a video, but it took too long to go through its booting steps.  The birds moved south and were blocked from sight.  Aargh!

Mississippi Kites are a common and widespread nester throughout residential New Orleans, wherever there are trees of sufficient stature to nest in.   From now through August, they will be the most common raptor in our urban skies- with the possible exception of the two vulture species, in some parts of the city.  They are one of our last migrants to return from the tropics each spring.  The first I saw in my hood was yesterday.

Black-bellied Whistling-Ducks have a puzzling history here in New Orleans.   They had been gradually expanding in our direction from Texas for decades, and had reached south-central Louisiana.  Then, a few decades ago, they seemingly jumped eastward over lots of potential habitat and suddenly established a presence in, of all places, Audubon Park.  Before long there were thousands loafing in the lagoons there.  They have continued to expand throughout southeast Louisiana.  While still reported in largest numbers at urban sites, they are becoming a common site in our rural surroundings as well. They have taken to nesting in residential areas of the city, presumably in tree cavities.  The birds harassing the kite this morning were presumably local nesters in my hood.

On a different, but important, note:    The next two weeks are usually the fortnight with the highest volume of bird migration through our area in the spring.  How many of the birds will land rather than passing over will depend on the weather- a cold front usually provides the best birding.