Refuge notebook: Refuge keeps a pulse on bird migration

This past weekend Bridge Access Road in Kenai looked like an early dipnet season on first-run kings. Every parking area was plugged and cars were parked haphazardly on the side of the road. The draw was not fish this time, but a rare opportunity to watch geese and ducks piling into small areas of open water next to the road. The bulk of the geese on Sunday were 7,000 to 8,000 Greater White-fronted Geese. Snow, Canada, and Cackling Geese also congregated in roadside ponds, along with a diverse group of several thousand ducks.


This spring many of the birds have been confined close to the road due to the late thaw. While the volume of birds seems much higher as well, it is likely the same number of birds that normally use the Kenai Flats during their normal 6-week migration period were cramming their movements into a much shorter time window. It’s the equivalent of the summer-long tourist season shortened to the first three weeks of July.

As a biologist, I am often asked to quantify how these “abnormal” weather events are affecting migration. But the reality is that in recent years the “abnormal” may likely be the new normal.

Several recent studies conducted by the Kenai National Wildlife Refuge targeted defining the dates of normal migration of waterfowl and shorebirds through our area. We conducted spring and fall aerial surveys of waterfowl using the Chickaloon Flats. During 2009 and 2010, graduate student Sadie Ulman also conducted ground-based shorebird surveys in the same area. Ultimately, there were several interesting patterns that were revealed in migration timing. The most obvious thing is that normal migration timing is constantly fluctuating due to weather.

Spring migration is relatively simple. Birds must get north to the breeding grounds as fast as possible. Often the limiting factor is snow cover at the refueling stops and breeding sites. The other major factor is whether favorable wind conditions exist to continue their flight north without exhausting the fuel supply.

Waterfowl and shorebirds employ slightly different strategies based on food preferences. While they both stop in similar habitats during spring, waterfowl target fresh vegetative shoots whereas shorebirds search for insects and worms. In normal years, waterfowl stream through over a six-week period peaking around the 29th of April. Shorebirds are slightly later with a peak around May 10th. It is amazing to watch these pulses if you get to see it change on a daily basis. One day there are 35 Western Sandpipers, the next day it is 150 and the day after that there are 1,700.

Migration in the fall is much different than spring. The complexities of fall migration are evident by the increase in the number of pulses. Instead of coming in one large wave that builds and then subsides, fall migration pulses, subsides, and pulses again repeatedly from early July through the end of October. The timing of these pulses is quite variable from year to year depending on weather.

The fall migration show actually kicks off with the southward shorebird migration in early July. These birds have not been in Alaska long enough to nest and rear young, so the majority are ones that failed to nest. During the week of July 5, 2010, over 80,000 shorebirds staged on Chickaloon Flats! This was the highest peak of that entire fall so it is a good indication that it may have been a poor breeding year with lots of failed breeders headed south already.

Throughout August and September, waterfowl and shorebirds just pulse through these estuaries. They stop for a few days and then one clear night with a southerly breeze blowing, everyone blasts off for the next stopover, likely in the Copper River Delta area. The process starts over again with the next wave arriving to the Kenai Peninsula.  

As the season winds down and things start to freeze up it seems like migration is all done. Then, in mid-October, we get the last big push of the northern waterfowl escaping before winter clamps down on Alaska. It is during these October waterfowl pulses that Chickaloon Flats may host as many as 12,000 geese each day!  

If you happen to find yourself at the end of Skilak or Tustumena Lake during this time, you may witness some impressive waterfowl congregations. I once got stuck at the east end of Tustumena Lake in a snow storm along with 10,000 Mallards and 6,000 Cackling Geese bobbing on the end of the lake. I think we all questioned the decisions that got us to that same spot.

Migration of these birds through the Kenai Peninsula is focused on hitting the prime feeding grounds at the Chickaloon, Kenai, Kasilof, and Fox River Flats. If you get a chance to visit one of these spots during a migration pulse you will be in awe at the number of birds using these valuable resources. There is nothing better than photographing a group of White-fronts dropping the landing gear, raising the flaps, and doing a controlled fall from the sky into a puddle next to one of the pull-offs at the Kenai Flats. If you miss it, don’t worry, the shorebirds are right on their tails.

Todd Eskelin, a Biological Technician at the Kenai National Wildlife Refuge, specializes in birds and has conducted research on songbirds in many areas of Alaska. You can find more information about the refuge at or


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