Last night afforded a great look at how weather effects nocturnal migration.  In the evening a storm front was approaching the Wasatch Front over the West Desert and Great Salt Lake.

At 8:57pm  the storm band stretches across the south end of the lake and out over the West Desert. There is a thin line of apparent migrants over the Wasatch already.  I have always assumed these were large flocks of sparrows lifting off at dusk this time of year.

The second frame is at 9:55pm and the storm front has pressed up over the lake and to the edge of Salt Lake Valley.  Migration over the mountains has picked up with some areas approaching 25-30dBz. IF you look at the south end of the storm there don't appear to be any migrants, and on the north end, migration is sparse.

At 10:58pm the storm was directly over the lake, valleys, and heading into the mountains.  Migration at this point appears to have been broken up pretty good by the storm. The northeast edge shows a good migration underway, and migrants still along the front edge of the storm. The south, west, and north edges appear to be pretty dead.

At 11:56pm the storm is directly over the valleys and mountains and appears to be breaking apart. Migrations is still happening in the areas where the storm isn't hitting, but its very light.  To the north and the south there is still no real movement, but to the west a large wave of migration appears to have started out over the West Desert.

One hour later at 12:59am the storm is over the mountains and moving towards Wyoming.  Clear skies to the west are favorable and the migrants have taken to the sky over the Great Salt Lake Again.  It's still fairly light at this point...

By 2:00am the storm is clear of the Wasatch Front, Valley,s and Lake and from here we can watch migration start to pick up over the next 4 hours before trailing off around 7:00am this morning.  This is fairly typical of storms fronts this time of year with migrants taking advantage of good conditions, and tail winds ahead of and following storms.  Below is a complete animation from 9:00pm last night to 7:00am this morning.

It's been a wild week of migration to say the least.  The beginning of the week saw our biggest flights of the year, while the middle of the week saw decent flights early in the evening that fizzled out shortly after midnight.  And last night put an exclamation on the week when migration was put to a halt by a large storm passing through northern Utah.

Let's talk about last nights storm:

This was taken just before 10pm as this massive cell passed over the lake.  For several hours it was very windy followed by the thunder, lightning, and then several hours of rain fall.  By about 3 am the storm was mostly cleared out, with the tail end to the east and north of the lake.

Quite the contrast to just a few hours earlier.  Had this storm come through a couple hours earlier or later, migration might have been a very different story last night.  I would expect things to start picking back up tonight, with decent movements as the weekend progresses.

The next three weeks will bring an onslaught of birds through our state as the height of passerine migration hits in mid May (or should hit in mid May).  Shorebird migration should start to slow down after this week.  Typically this last week of April brings in some of the best shorebirding of the year.  The past couple of years shorebird migration has peaked later into May providing great shorebirding through the middle of the month.  Based off current trends I would speculate this year will be more on par with the usual migration patterns and things should start to slow.

Last night was another superb night of migration over northern Utah.  The favorable conditions certainly are lending a hand to keeping things moving.  As I ogled the radar last night it was awesome to watch the stream of birds leaving the north end of the Great Salt Lake and heading off into Idaho.  Large numbers of birds in the 20-25 dBz level could be seen rising then heading north and dispersing.  Based off the density it is presumed that there are approximately 200-600 birds per km cubed where it reaches this amount of reflectivity. (via Clemson BirdRad).

I have put together an animation that starts at 9:00pm last night and lasts 90 minutes.  Check it out:

Just watch for the green to appear around 3:24 UTC and move northward till it blends into the blue around 4:02 UTC.  Pretty cool to see that high density of birds as they move north from the lake and north end of the Wasatch.

I expect there to be a fair number of new shorebird arrivals today given the movements last night.  Plus it's about time for some of the big waves of Yellow-rumped Warblers to be coming through as well.  Yesterday I had my first Yellow Warbler of the year as well as a Lazuli Bunting.  Reports of Bullock's Oriole, Thrushes, and other migrants have also been coming in.

Interestingly last night, I saw what was one of the coolest radar images I can remember.  It was the showing the entire US, and what was cool/odd about it was the fact that the Midwest was exploding with migrants, while the east half of the country looked just like the west half with very little showing up on the radar:

Typically this time of year the entire east looks like the Midwest, but last night migration in the east came to a crawling stop.  This could be in relation to the storm that passed through, but I'm not sure if that is the whole story seeing that everywhere from Florida norther to Maine, and the Carolina's west to Missouri were all effected.  In any event it made for a rather cool radar image--that makes me wish I were birding in Texas today!

Last night and the night before we were again treated to light migrant movement.  Storms came in across the lake both nights keeping the majority of birds either below the radar or completely out of the sky.  Two nights ago there were more birds in teh air than last night.  I put together this animation showing what happened between 8pm and 4am.  You can see migration pick up as the sunsets, but then it comes to a halt as the storm hits the lake.

The other cool thing you can see in this image is the storm coming in from the west form near nothing to completely filling half the screen.

These storms are certainly keeping the majority of migrants out of the sky at night--but that could all change this evening.  According to the Weather Service, the storms are supposed to push through the Wasatch Front today and tonight will be partly cloudy--followed by 3 mostly clear nights (and great nights for night migrant listening with temps in the 50's)... Plus, the next 4 nights also happen to center around the new moon.  There are potential ups and downs to this.  The plus side being that there has been evidence presented that the moon can interfere with with stellar navigation. So no moon may mean that more birds are out--although this is purely speculation and has no real science backing it up.  The major downside is that it makes it harder to find your way through the dark.  It also means that if you were planning on scoping the moon to try and watch for passing migrants, you can't.  No moon won't effect your ability to listen for night flight calls though!

On a side note, with the new moon being this week, that means that May 1st through May 15th will be nights filled with plenty of moon, so if you wanted to test out scoping the moon for passing migrants you could (I personally will be trying to pick up my first Flammulated Owl of the year I think!).

So above I mentioned scoping the moon, and some of you may be left scratching your heads.  I haven't really touched on this before, only because I have never had much luck with it, but many observers back east can attest to the fact that you can see migrants even a couple miles above the Earths surface passing in front of the moon.  I had a friend from Michigan who on multiple occasions shared stories of doing this from his yard.  I may give it a whirl here in a few weeks once the moon is out in full force again.  If any of you try please feel free to share your comments on the blog and let others know form where, what time, and what kinds of numbers you saw.

Anyways, back to the radar.  Last night was a far lighter night of migration than the previous night but still there were a few birds moving.  Something interesting that I noticed was the line of birds apparently over the Wasatch Range on the east side of the Great Salt Lake.

This is something that I have noticed in the past and appears to be pretty common during both the spring and the fall.  One assumption is that these could be sparrows, and other forest birds starting to arrive,  They could be wintering species heading back north.  Something that many wouldn't think of but makes a lot of sense right now would be migrating loons.  Possibly hundreds moving over the mountains right now as they head north to breed.  As you watch the radar the next couple of weeks look over the mountains and see if you notice any patterns.  As migration picks up it may be harder to actually pick this line up as there are going to be hundreds and thousands of birds up there.

Another reason I am pointing this out is that it may be worth your while to listen for night migrants at higher elevations.  A few years ago when Colby Neuman and I would listen for migrants around Salt Lake we tried a number of locations.  Almost always it was higher than the valley floors but not way up in the  mountains.  The hills above the State Capitol Building, and South Mountain were 2 places we tried.  Colby tried a few other high elevation areas, and I did a couple nights over 9000' feet in the Uintas.  The best night I had listening for migrants in Utah was at 9400' in August 2007 in the mountains south of Strawberry Reservoir.  Overall however it's always a mixed bag, or like Forrest Gumps mama always told him, "you never know what you're gonna get".

I will leave it at that for now, good luck listening for night migrants--let us know if you're hearing anything!

This year I've decided to try and post about spring migration in Utah at least a couple times per week.  Most of what I am going to talk about is nocturnal migration by radar--with some followups of actual day time migration birding.  I will try to keep up with this until the end of May.  I decided to start in mid April because March and early April migration is so light.  Plus at this point we are getting in to heavier passerine migration.  So let's get started.

I have been periodically checking the radar the last couple weeks.  There hasn't been much in terms of birds moving, but there has been plenty of weather.  Last night was the first night over the last couple weeks where there were actually birds visible on the radar.  Below is a compilation of the previous 5 nights (April 12-16th):

The large masses are storm systems moving through late last week.  The two images with smaller masses are also weather, but much just small storm bands moving through the past few nights.

I was beginning to think I wasn't going to seen any migrants on the radar anytime soon--but last night that changed:

I added labels pointing out the birds on the radar and the weather.  If you want to learn more there are some links at the end of this post that go to past posts where I explain how to read the radar.

Migrants were light last night, but at least they appeared on the screen.  This image is from just before midnight--to be consistent over the next few weeks I will try to be consistent and use images from this same time frame.  However, if something cools shows up I will definitely show images for other times.

I also took a shot of the velocity screen to show something:

You can see that the birds in the center of the radar are headed due north at more than 10 knots, while the storm appears to be moving north east at about 5 to 10 knots (1 knot = 1.15077945 mph).

We can assume based off the radar that a few birds were trying to move north as the storm approached.  By 3am migration was all but over for the night as the storm hit the lake.  It's hard to say what types of birds these were, though given the timing shorebirds are likely.  Hopefully, in the coming days as the storms move out and better weather greets us, we can get a few nights with some heavier migration.  In a couple weeks it will be full on passerine migration and the radar images should be chock full of birds.

As I mentioned above here are some more resources for Nocturnal Migration and Birding by Radar:

Utah Birders Blog: Nocturnal Migration Part 1 - Introduction

Utah Birders Blog: Nocturnal Migration Part 2

Utah Birders Blog: Nocturnal Migration Part 3 - Base Reflectivity

And if you are interested in looking at the radar at night you can check it out here:

NEXRAD images from WSR-88D radars

and also here:

National Weather Service Radar