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The Peregrine Fund Notes From The Field
2011 South Texas Artificial Nest Structure Work
Paul Juergens — in Aplomado Falcon Restoration    Share

The days are getting longer, temperatures are climbing, and the wind is making a regular presence tossing up dust and tumbleweeds; doing its best to make working outside miserable…winter is coming to an end and spring in southern New Mexico has arrived. It is time to work on aplomado falcon nest structures for our southern Texas population. Building the nest boxes has always been a very enjoyable part of the job. It sort of reminds me of those childhood projects of building bird houses, chicken coops, benches, etc. Simple yet very effective. When it comes to aplomado falcons, many of these artificial nests are not totally necessary in coastal Texas where the population appears stable and where natural nests, built by other species like white-tailed hawks and Chihuahuan ravens, are abundant. However, what the nest structures do provide, now that we have seemingly worked out their design to its maximum effectiveness, is a very safe place for falcons to nest and ultimately improving nest success and productivity in the population – a scenario often not offered by many natural nests. Essentially, our breeding pairs of aplomado falcons, particularly those utilizing nest boxes, are working as miniature hack (release) sites that at the very least during difficult years (e.g. droughty periods) are apparently able to keep the population at a stable level so long as habitat is available. We can make this statement as we have found recruitment rates of wild fledged young are much higher than that of captive-bred released falcons. So the beneficial role the nest structures provide cannot be overstated.

Brian walking out to check a nest structure on Matagorda Island NWR - Photo by Paul Juergens

During the last two weeks of February and first few days of March, Brian and I made a trip to southern Texas starting at the northern end of the recovery area on Matagorda Island National Wildlife Refuge (NWR) to check existing nest structures and replace a few old worn out nest structures with new ones. Our next stop was the Rio Grande Valley where we continued with this work. We eventually met up with Tom Cade and Grainger Hunt along with friends and colleagues with the U.S. Fish and Wildlife Service and National Wildlife Refuge System to discuss the habitat requirements of the falcon in this region and see examples of prime falcon habitat like that along the infamous “Old Port Isabel Road” where many observations by birders and enthusiasts of the aplomado falcon are made. This information will assist land managers in identifying additional habitat as well as developing a plan to improve and/or maintain existing occupied habitat and perhaps even create more habitat for the falcon. Each year it becomes increasingly apparent that the coastal habitat falcons are currently occupying is the number one stronghold of the species in the United States, and with the management of prairie habitat in this region, a sustainable falcon population should endure for years to come.

Team with a just finished aplomado falcon nest box.

Pictured left to right are Brian Mutch, Brian Millsap, Grainger Hunt, Tom Cade, Tim Anderson, & Paul Juergens - Photo by Brian Mutch

In closing, we visited most every territory in our two main population areas to inspect and maintain existing nest structures as well as replace some of the older nests that are nearing their expiration. Of the 39 nest structures/territories visited, most were in very good condition and needed little to no service. Generally, we would only have to add a small amount of bedding to the nest as added substrate in which the falcons will make a scrape. Four structures required a new nest and substrate; three territories were provided new nest boxes. Of particular interest, we were unable to service a nest structure in a territory we call La Clinica because, to our surprise, we found the territory not only occupied but the female in the nest was incubating. This is one of the earliest observations of falcons incubating in S TX. We observed eight pairs of falcons and eight individuals on this trip. Aside from a little delay in getting some needed supplies for the nests and Brian almost getting bit by a venomous snake, a North American cottonmouth snake (struck the bottom of his boot), the trip went rather smoothly and a lot was accomplished. Next on the agenda is the spring falcon territory occupancy and nest survey. Be sure to check back for future updates! Adios!

A young bobcat at the Laguna Atascosa NWR - Photo by Brian Mutch

Adult aplomado falcon on older, open platform artificial nest structure - Photo by Brian Mutch

On Laguna Atascosa NWR, we observed these two male western diamondback rattlesnakes in "combat." The purpose of this combat during the snakes' breeding season is to determine which is the dominant male who ultimately gains the breeding rights with a female rattlesnake if one is nearby.

- Photo by Brian Mutch

Photo by Brian Mutch

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