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Birding Home | Access Updates | RBA | Dastardly Duos | Know Your Habitat | AZ/NM Listserv | Tucson Area |
Tucson Audubon Society
Know Your Habitat
by Larry
Liese
See the Know Your
Habitat home page
Articles in this series first appeared
in the Vermilion Flycatcher, newsletter of the Tucson Audubon
Society. To receive the newsletter, join the Friends
of Tucson Audubon.
Habitat 2: Wastewater Treatment Plants
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Ah, let’s go birding today! Where should we go? How about a trip to the Green Valley Sewage Ponds? New birders joke a bit about this category of birding destination, but wastewater treatment plants provide an important resource for our avian friends, and are heavily used by migrating shorebirds and wintering waterfowl. Anyone participating in a Christmas Count or Birdathon Big Day knows that these are the only places to find certain bird species.
The waste treatment process relies on storing large quantities of water for some time to allow microbial action to reduce the nutrient content of this water to levels appropriate for discharge into our river drainages. With groundwater pumping for agriculture and human consumption, this effluent flow has become the sole source of running surface water in many instances. These resulting riparian stretches, though not covered in this series, are another important vegetation community for birds.
The same nutrients that the wastewater treatment plant desires to eliminate in the partially treated wastewater are the base for a food chain attracting the birds. Small organisms growing in the water are both consumed directly and also feed invertebrates that attract a variety of birds to both mudflats and deeper waters. Since many birds’ bills are specialized for harvesting different food resources in different microhabitats, we see a wide variety of bird species at various times of year.
Wintering waterfowl such as ducks travel south each winter as ice covers their breeding ground ponds and lakes. Sewage ponds provide a resource not easily found in our area, and hundreds of individuals of some duck species will winter over in a single site. Northern Shoveler and American Wigeon are probably the most numerous, with more than fifteen other species possible.
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One has to keep up a steady visiting cycle to not miss the shorebirds that visit wastewater treatment plants, as many are here only as migrants and sometimes ‘one-day-wonders’ that don’t stick around. About twenty shorebirds are listed as rare or better on our southeast Arizona checklist. If you’re like me and keep a cumulative list of the ones you’ve seen in the checklist area, frequent stops during shorebird migration might get you a new species. When to go? Look up the bar charts in the local Tucson Audubon or ABA area guides. If you’re interested in a particular species it might be earlier or later, but in general the best spring months for migrant shorebirds are April and the first half of May, with a wider period centered around August and September best for fall. Look closely at whatever birds are present, being careful to note if one bird looks a little different. Comparing sizes with adjacent birds is a good place to start when working an unknown target. Bill size and shape are important, as well as leg color—a tricky field mark at times. And, oh yes, nearly all of them are light on the bottom and streaky brown on top; have patience!
Raptors are usually prevalent around waste treatment plants, due to the sometimes-abundant prey available to them there. Osprey, Northern Harrier, Sharp-shinned and Cooper’s Hawks, Red-tailed Hawk, Kestrel, Merlin, Peregrine and Prairie Falcons can all sometimes be found looking for a meal.
In recent winters, longspurs have sometimes been found north of the entrance road before reaching the water impoundments. Look closely for these easily missed birds. Also in winter Lawrence’s Goldfinches can sometimes surprise you. Look in trees along the entrance road or around the Pima County Maintenance Yard just short of a mile south of the entrance road turnoff.
If you plan on visiting one of the local wastewater treatment plants for a birding outing, a few notes on birders’ responsibilities are appropriate. Be sure to sign in at the office. Read and follow all notices and restrictions posted. Keep away from new construction and any machinery or equipment. Stay up on the top of roadways—do not walk down into any of the water-holding areas. Don’t arrive before stated opening times and please be off the premises well before their quitting time. Let’s keep treatment plants birder-friendly!
What’s next in this series? In the May/June issue, we’ll get to our first natural habitat—Sonoran Desert scrub, a vegetation community that hosts many of our favorite desert birds.
Bird questions? Check Birding | General questions? Contact: Tucson Audubon Society | Webmaster: Email
This page was updated on 02/21/06