Bird tally at Ivanpah in March ‘13

ReWire discusses the March 2013 compliance report from Ivanpah Solar Electric Generating System: Bird Deaths Continue at Ivanpah Solar.

Mr. Clarke summarizes the report by explaining that in March, 22 of 55 dead or injured birds were clearly injured by the solar flux. Most of the rest were sufficiently decomposed that the cause of death couldn’t be determined.

Mr. Clarke is concerned the heat may be so high that there isn’t enough left of smaller birds to identify them at all. Any such birds in that category wouldn’t be included in the official count.

The March casualties took place while the facility was operating at 55% of capacity, according to Mr. Clarke’s research. The mortality will likely be higher when the plant sustains maximum output.

The compliance report for March can be found here. I browsed through it, although at 967 pages, there is a bit too much for me to absorb. A lot of it is way over my head.

I looked at table 9 of exhibit 9 on page 890. That lists the avian mortality and injury for March. I noticed a few things of interest to me.

There were a few birds (8) found from a carcass survey early in the month.

Once a month survey?

Of far more interest to me is the end of the month. From March 25 through March 31 there were 30 birds found in a carcass survey. I didn’t double check my count, so I may be off. That sounds like it was a several day project to cover the whole facility. Of particular interest is the length of time the birds had been dead. The estimated time of the injury or death before being found is listed for each bird. Here’s what I counted:

  • 2 – under 8 hours
  • 2 – under 1 day
  • 8 – 1 week
  • 2 – 2 weeks
  • 13 – 3 weeks
  • 3 – 1 month

Most of those were found near the heliostat.

That age distribution tells me there is essentially one survey a month. Maybe once every three weeks (but that would mean the previous survey missed a bunch of birds).  Most of the birds have been dead for 2 or more weeks when the survey found them. Half had been dead for 3 or more weeks.

The question that reinforces is how many birds get eaten up or carried away in the weeks between surveys? Foxes, coyotes, and ravens have little ones to feed (of course maybe I just don’t know when the babies are able to go out hunting with mom or dad – anyone care to enlighten me?) so it seems they may take dinner home with them. Ravens could carry off the smaller birds.

Again the question: how many birds get missed between the surveys?

Seems to me the official count is a minimum of the avian mortality.

Cause of injury

The report gives the suspected cause of injury. In March there were exactly two birds killed by collision.

There are only two other causes of death. First, ‘scorched or singed’. The only other cause of death is ‘unknown.’

Let’s back up to the tally mentioned in the article of 55 injuries/deaths of which 22 are burned. Back out 2 deaths from collisions, that leaves 31 birds in such bad condition that cause of death can’t be determined.

If it were possible to determine the cause for the 31 that are unknown, I’ll guess the overwhelming cause would be getting toasted.

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