Weather pushing birds north as we speak

The following was posted a couple of days ago on the eBird web page maintained by the Cornell Lab of Ornithology. The lab is working with the National Oceanic and Atmospheric Administration to predict bird migration northward as created by weather systems. It's February, but spring migration is underway.

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Watch for a good migration of birds up through the Great Plains on Saturday night and Sunday. As the weakening storm moves eastward, we can probably expect some bird movement through the Great Lakes and maybe even the Northeast on Monday and Monday night, but it is not likely to be nearly as strong.

The combination of a high pressure system moving across the eastern United States Saturday and Saturday night and a low pressure system tracking into the northern Plains is leading to a strong pressure difference across the Plains. It is this difference in pressure that drives the winds. Since high pressure has clockwise flow and low pressure has counter-clockwise flow, this is a recipe for strong south winds up the central Plains Saturday night and Sunday. The atmosphere often organizes wind into corridors or "jet streams". Many of you have heard about the jet stream and often think that these only occur at high altitudes hence the name "jet" stream. However, the atmosphere also produces these jet streams in the lower atmosphere... There was a wind forecast for Sunday morning between 1000 and 2000 feet above ground, which is about the height at which many birds are probably migrating. The storm system will weaken as it moves eastward to the Great Lakes, and the strong lower level jet stream will weaken by Sunday Night and Monday as it shifts into the Ohio Valley.

The exceptionally warm winter across much of the Eastern US means that migrants may be on the move earlier than usual this year, and we are already seeing this in many places (see Woodcock and Killdeer below). Many facultative March migrants are likely to be ahead of schedule, and record early arrival dates could occur given this combination of a warm winter and an early blast of warm air. So get out there and see what you can find! Below are some of the species groups to watch for as this unusually early blast of warm air sets spring bird migration in motion. If you live in the southern United States or Mexico, you might watch for the early departure of some of these birds.

Geese and swans – Snow, Canada, Cackling, Greater White-fronted, and Ross's Geese should all be on the move with this weather system. Watch for them to potentially move north to staging areas in Nebraska, and possibly to Quebec and points further east. There is also a possibility that some western geese (Cackling, Greater White-fronted, and Ross's) could be displaced eastward with the strong southwesterly flow. Watch also for Tundra Swans departing the mid-Atlantic and heading up through the Great Lakes.

Ducks – A range of puddle ducks and diving ducks could be moving, including Mallard, American Black Duck, Northern Pintail, Green-winged Teal, Canvasback, scaup, Bufflehead, and many others. The first arriving Blue-winged Teal and Wood Ducks may also appear. We expect waterfowl concentrations primarily at traditional staging grounds. Also watch for species like Northern Pintail in flocks of northbound Snow Geese. Since there is no significant rain forecast, inland duck fallouts are unlikely.

Osprey – In many areas where Ospreys don't winter, they return in March, with exceptional arrivals (on the East Coast, at least) back at nests by late February. If you need Osprey for your local February list, this year could be your best bet!

Other Raptors – Many hawks are on the move already in late February and March, and with conditions like these, the Great Lakes hawkwatches (e.g., Hawk Ridge (Duluth, MN), Braddock Bay, Derby Hill, and others) are apt to do quite well, depending on the daytime winds at each site. Many Rough-legged Hawks (and possibly a few Snowy Owls) will use this weather to move northward, along with Golden and Bald Eagles and Red-tailed Hawks. Northern Goshawks could be on the move through the Great Lakes region.

Killdeer – A late February/early March migrant, we are already seeing Killdeer on the move this year. Check out the 2012 January map compared to the February one and note the incursion into the upper Midwest. We can certainly expect more Killdeer with next week's weather, setting up an earlier than average arrival across a broad front.

American Woodcock – Woodcocks typically move into mid-latitudes starting in late February, with arrival in more northerly states in mid-March. Many places (as far north as Maine!) are already seeing pioneering woodcocks up to three weeks ahead of schedule, and like Killdeer, this pattern can be expected to continue. Watch for them in the evening in areas where old fields mix with younger woodlots. On calm evenings, you may hear them 'peenting' and displaying.

Belted Kingfisher – Arrival in the northern half of the country usually begins in mid-March, but many have wintered farther north this year due to the unusual amount of open water. This could be an interesting species to watch; will their migration begin two weeks early given the mild winter and favorable winds?

Sparrows – This early in the season many sparrows are stealthy migrants whose migration is difficult to discern. Song Sparrows and Dark-eyed Juncos are two species that could be on the move, both of which are often ignored since they winter widely. Watch for both species in higher numbers or in areas where you haven't seen them this winter. American Tree Sparrows could start withdrawing back to the north, and Fox Sparrow is a well-known early spring migrant, with movements well underway in March.

Blackbirds – Species such as Red-winged Blackbird, Common Grackle, and Brown-headed Cowbird are the first signs of spring migration in many places, usually first appearing in February. Look for legions of blackbirds to move north with this system.

As birds are headed north in spring, southerly winds helps them along. The longer it continues, the more birds will arrive. However, the best conditions for birders to witness migration occurs when favorable weather occurs in pulses interspersed with unfavorable weather; this causes birds to move en masse on the first break in the weather. Many birds wait until favorable southerly winds develop before initiating migration, and when the right conditions occur, large migration events often happen. Of course good migration days don't always mean that you will notice the migration, since much of the movement occurs at night for passerines (landbirds), waterfowl, and shorebirds. You might hear flight calls overhead at night (especially geese, shorebirds, and sparrows), and might see some movement of geese and raptors during the day, but in other cases you are most likely to notice that the selection birds at your local patch seems to have changed overnight.