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The Peregrine Fund Notes From The Field
1 - 15 July 2003
Sophie Osborn — in California Condor Restoration    ShareWhen tourists view condors at the South Rim for the first time, the awe that they feel is quickly followed by curiosity about these giant birds and the efforts to restore them. After we explain that we monitor the birds all day, every day using radio telemetry, the invariable follow-up questions are “How long do the batteries in the radio transmitters last?” and “What do you do when the batteries die?” Since the batteries last about a year, the answer to the second question is that we must retrap the birds to replace the transmitters. This response is always followed by a look of amazement and disbelief and an exclamation of “How on earth can you catch a bird like that?!”

Fortunately, for the condor field crew, trapping condors has become fairly routine. Whereas we used to take down our condor trap after each trapping session, we now leave it in place at our release site year-round. This gives us the flexibility to trap a condor at a moment’s notice. Since the wire trap has become part of the birds’ environment at the release area, the condors are unafraid of it and pay it absolutely no attention, unless it contains a carcass. Trapping the condors is also facilitated by our having a large number of naïve juveniles in our condor flock. These youngsters are generally far less wary than the older birds and readily enter the trap to feed. Luckily, seeing other condors feeding on a carcass is an almost irresistible draw for the warier adults.

During a trapping session several years ago, we ended up holding all our juveniles (and many of our older birds) in our flight pen. Trapping the last remaining adults in our population with no juveniles out there to draw the adults into the trap took weeks. Indeed, we never did trap two of the adults during that trapping session. Such a scenario is likely more akin to trapping condors in the late 1980s, when biologists spent months trying to trap the last remaining adult condors in the wild to bring them into captivity to form a captive breeding flock.

Leaving our condor trap out year-round and assuring that there are juveniles around has greatly facilitated our efforts to trap target condors. Nevertheless, while trapping several condors is relatively easy and trapping a target bird is usually doable, capturing the entire condor flock is another matter! And one that takes a great deal of time and effort. During the months of June and July, we set out to do just that, in order to vaccinate all our birds against the West Nile Virus.

We had successfully trapped more than half of our free-flying condor population in June. Catching the remaining birds would be harder since the remaining birds return to the release site more sporadically than those condors already trapped. We would need to bait our trap whenever birds that we needed returned to the release area. On the night of July 1, several condors that had yet to be inoculated returned to the release site for roost. After dark, Project Director Chris Parish once again baited the trap and readied if for its early morning opening. (We always bait the trap at night while the condors are sleeping on the cliffs so that they do not associate us with providing them with food.)

By mid-morning, Chris closed the trap on two target birds, adult Condor 134 and juvenile Condor 249, as well as on five other juvenile condors that had already been inoculated. Our delight in being able to confer a measure of protection from the West Nile Virus on the two target birds was quickly overshadowed by the fact that both had elevated lead levels. Condor 249’s lead levels were moderate, so we transported him to our flight pen for monitoring. We would retest his blood in a few days to determine if his lead levels were on the increase or decrease. Unfortunately, Condor 134’s lead levels were high. Quickly, we shut down the trap and prepared poor Condor 134 for his journey into Page, Arizona for an X-ray.

A few hours later, we breathed a sigh of relief upon discovering that he had no lead fragments in his system. Nonetheless, he would need to be held and chelated (treated with a series of 10 injections to remove the lead from his system). We transported Condor 134 to our new condor treatment barn, which had been vacated only recently by Condor 133. On the evening of July 2, we began Condor 134’s first round of chelation.

Over the next week, plans to continue trapping were unexpectedly foiled because of a large food bonanza that materialized at the South Rim of Grand Canyon National Park. On July 4, a cow elk fell from the cliff rim to her death near Grand Canyon Village. Condors discovered the carcass the following day and were soon streaming into the South Rim area. By the afternoon of July 5, 16 condors were squabbling over the feast, access to which was still limited by a very tough hide.

The demise of the cow elk kept the majority of our condor flock tied to the South Rim area for days. On July 8, 28 condors roosted near the Grand Canyon Village! To our delight, our two parent condors, Condors 123 and 127 fed voraciously. The elk carcass was only a few miles from the pair’s nest cave and hungry chick. After filling their crops, the two parents periodically headed back toward their cave, disappearing from our view.

The pair continued to be wonderfully attentive to their nest during the first half of July. On several occasions, male Condor 123 flew to the release area from the South Rim, fed, returned to the nest cave, presumably fed his chick, then returned to the release area – a total distance of more than 150 miles - all in one day! Typically, at least one parent spent time in or near the nest cave, interspersed with making food-finding forays, while the second parent ranged farther afield. On some nights, however, neither pair returned to the nest. Such behavior is completely normal for a bird that has to travel so widely to find food. Now that the chick could thermoregulate on its own (meaning it did not need its parents to keep it warm), the parents had more freedom to travel and search for food.

After finishing up the elk, Condors 123 and 127 appeared to join other condors in finding and feeding on two additional carcasses between the North and South Rims. Unfortunately, the condors’ ability to travel to wildly remote and inaccessible areas often means that we are unable to document what they might be feeding on. Although the birds reappeared with full crops on both occasions, we did not have an opportunity to identify the food items.

Despite doing everything we hoped and dreamed of him as a parent condor, Condor 123 nevertheless caused us incredible anxiety by going into “stealth mode” on July 7. Coined by ex-condor field crewmember Blake Massey, the term “stealth mode” means that neither of the two radio transmitters worn by a condor functions and the bird is therefore undetectable using radio-telemetry. One of Condor 123’s radios had stopped transmitting months earlier, but we had not wanted to cause him undue stress by trapping this first-time parent to replace it. On July 7, crewmembers Roger Benefield and Jason Blackburn, who were watching Condor 123 picking at the remains of the fallen elk carcass could not pick up the signal from Condor 123’s second transmitter. (Each condor wears two transmitters, so we can still follow them in the event that one fails.)

As the most dominant condor in our flock and the father of our chick, Condor 123 is arguably the most valuable of our condors. All we could do for the time being was cross our fingers and hope he would return to the release site where we would be ready to trap him at a moment’s notice. In the meantime, we kept thinking about the tremendous loss experienced by the California field crew last year, when their dominant condor and father of one of their chicks, disappeared. His conventional transmitter had stopped functioning a few weeks earlier. Although he also carried a satellite transmitter, it was solar powered, so would not have functioned had the bird fallen into a dark crevice or landed on top of the transmitter. I couldn’t help but imagine Condor 123 meeting a similar fate and disappearing into the immensity of the Grand Canyon forever.

Such dire thoughts lurked in the backs of our minds as we made yet another attempt to trap condors that still needed to be inoculated against the West Nile Virus on July 15. Although we did not trap Condor 123, we did manage to trap one new condor, Condor 203, who also needed new transmitters. Sadly, Condor 203 had moderately elevated lead levels and we transported him to our flight pen for temporary holding and monitoring. Trapping our condors for West Nile Virus vaccinations had given us a far grayer picture of the state of the condors’ (and our!) world than any of us had envisioned. Clearly more lead was present in the environment than we had ever supposed, if so many of our condors were showing elevated lead levels as a result of their summertime wanderings. For now, all we could do was keep a close watch over our condor flock and continue our efforts to identify sources of lead in our condors’ environment.

Until next time….

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