2010 Sacramento population declines again, but only slightly

[Daniel Airola]

The martin breeding season is nearly done here this year, so we have close-to-final population information. Since 2002, my colleague Dan Kopp and I have monitored 9-12 colonies that breed annually in elevated freeways and overpasses ("bridges") in urban Sacramento. This population is the last remnant of a once widespread population in the Central Valley, which was otherwise eliminated following starling arrival here in the late 1960s.

This year's population declined again, for the 6th consecutive year. This year we had 68 pairs, down 3% from 70 pairs last year. Overall, the population has declined by 61% from the 173 pairs we had as a high population in 2004. The number of active colonies remained at 9, but several colonies are down to 1 or 2 pairs. The only bright spot is that the rate of decline from the previous year is the lowest since the decline began in 2005. Also, we saw what we think is a substantial late pulse of SY breeders this year, though we have not rigorously compared SY pair numbers to previous years.

The ultimate causes of the long-term decline, and its moderation this year, are uncertain. Conditions were dry over the previous few years but we received average rainfall this year. We continue to observe what appears to be a high level of train, truck, and car mortality, with 5 adults found dead this year, and an unknown number of additional birds presumably not found. This mortality factor may be intensifying as Sacramento focuses on "infill" development to reduce traffic, energy use, climate effects, etc.

Once again, we were unable to attract martins to use nest boxes away from sources of urban mortality. The boxes have been up for 3 seasons now with decoys and a dawnsong player. We have boxes in ideal wetland refuge habitat, but it is located 5 miles from known colonies. Boxes placed at one bridge colony were used for perching, but not nesting. Another set of boxes erected this year near a bridge site that attracted martins once 7 years ago also was not used. Presumably the population is not productive enough to encourage a lot of new colonists to seek out a new nesting substrate away from existing colonies.

At least we may have bought a little time this year in our race to try to get martins into less risky habitats.

[Steve Kroenke]

Hey Dan,

Thanks for the update on purple martins in the Sacramento area. I know it must be disheartening to see a decline in the population since 2004 though the decline this season was small.

This season we lost a large number of martin fledglings on the road in front of our colonies. The fledglings would land in the road and fly up and down it as if they were trying to skim "water"; perhaps the asphalt looked like water to the youngsters. I found as many as 15 dead ones in one day. So martins can be vulnerable to motor vehicles in certain areas.

I know that some folks are having success with gourds and single unit wooden boxes in parts of Washington state. There have been several postings lately on the Forum.

I appreciate all the hard work you, Stan Kostka and others have done to help the martins out west.

Steve

[DelmaWhisenhunt]

Dan, I read with interest the information you shared of the purple martins especially in Sacramento. My husband and I lived there for a number of years, but never picked up the interest in martins. Of course he drove freight line and was gone much of the time. His brother John was a long time doctor in Sacramento. We all came from Okla., raised in rural farming area and saw martins/ however we took them for granted. Of course I didn't share the love of martins till about five years ago and have not been a successful land-lord, but I am still working at the dream. Again I read your note with much interest. I still have nephews living in Sacramento, maybe I can encourage them to take note of the beautiful purple martins.

[Daniel Airola]

Thanks, Steve. I read your previous post re: martin use of roads. We haven't ever seen anything like that here. Our birds frequently perch on the electrical wires for the light rail trains, and though they normally move when the trains come, the trains come every 10-15 minutes all day long, so it is risky. Many of the sites where martins nest are under Interstate 50 and 80, so any mortality there is basically impossible to detect (too unsafe to conduct surveys and any carcasses don't last long). We find only those that get knocked off the roadway and fall to the area below.

Hi Delma. If you noticed the martins when you lived here, you are one of the few!. Because they are so rare, except for the birders, most people here don't have any idea what a purple martin is. We've tried to raise their profile through media stories, with limited success.