We drove into Moonglow Dairy on a dusty dirt road, scanning for blackbird flocks. We passed muddy cattle pens with little grass or other vegetation and looming heaps of compost. Even the leaves of the distant eucalyptus grove were brown with dust. Completing the picture, black phoebes hunted from the tops of leafless bushes. When we stepped out of the car, our faces contorted as we smelled hundreds of cows at close range. Cows stood in lines behind their food troughs, eating through piles and piles of slimy vegetables — which did not smell so great either. Flies swarmed in thick clouds around the cows and their rotting food, doing nothing to improve the atmosphere.
We were at this stinky cow farm to see a bird, specifically the tricolored blackbird. They have a fairly small range, mostly in California — making them an attractive target for birders from the east coast — although they also have scattered breeding colonies in Oregon, Washington, Nevada and Baja California. Tricolored blackbirds breed in large communal colonies in fresh water cattail marshes, but they seem to gravitate to more artificial habitats for foraging, such as fields and cattle pens in their range.
Tricolored blackbirds look very similar to a much more widespread species, red-winged blackbirds. Males of both species are medium sized, glossy black and have a red patch on the shoulder bordered by a light-colored stripe. Females are streaked brown and white. The only field mark our field guide gave to separate males of the two species was that on tricolored blackbirds, the light line was supposed to be white, while on red-winged blackbirds it was supposed to be yellow. The book did warn that the shoulder patches of freshly molted or molting male tricolored blackbirds could look more yellowish though. Not much to go off, as we soon realized.
We got our birding stuff and braved the foul air and flies, walking slowly up the road. We saw a few blackbirds, but they were mostly hidden from view by small hills. Most of the ones we could see clearly were Brewer’s, although there were some with thick yellow stripes on their shoulders. As far as we knew, tricolored blackbirds should have white next to the red on their shoulders, so we decided that the birds we saw with the thick, yellow stripe must be red-winged rather than tricolored. Even so, I was pretty sure I had never seen a red-winged blackbird with this much yellow on the wing and so little red. Could it be a plumage I didn’t see often, such as that of an immature male? Just as we were coming to this conclusion, a huge mass of blackbirds lifted off from behind a distant barn and descended into the cattle pen in front of us, totally swamping the few birds we had been struggling to see before. Of the hundreds of birds now present, almost all had the thick yellow stripe, while a few had a massive red patch and almost no lighter color at all. Surely all these birds couldn’t be immature male redwings. We decided that the tricolored and red-winged blackbirds must be distinguishable from each other based on the relative whiteness of the “yellow” stripe rather than on a clear categorical difference.
At that point our search became farcical. My brother Theo started pointing out birds with light colored stripes that he thought were whiter than those on the birds surrounding them. Unfortunately, I could see no decisive difference between the birds he claimed were tricolored and the birds that looked exactly the same to me, that we agreed were red-wings, sitting right next to them. He pointed out bird after bird with supposedly whiter wing stripes. Even the act of finding his birds amidst the mass of feeding blackbirds was a struggle. He would zoom our scope in to its maximum distance and attempt to convey the location of the bird he wanted me to look at with land marks as unpredictable as which way the fattest pigeon in the scope view was facing. Inevitably, just as I thought I had found the right bird, the entire scope field would be taken up by the curious head of a cow.
Theo grew impatient with my inability to see the birds with obviously whiter stripes and I grew more and more frustrated. To make matters worse, my parents, who sometimes still cannot identify a bird as striking as a pelican in flight, chimed in that they too saw birds with whiter stripes than others. What the heck was going on? Was I suddenly color blind? I didn’t think so, but it was hard to rule out the possibility. I know it’s silly, but I particularly can’t stand my little brother getting a bird that I miss. It doesn’t happen often, but when it does it hurts. He saw a bananaquit in Florida, for instance, while I was scanning the wrong bush for it. The bird spent half a second in the bush Theo was watching, and then disappeared, never to return.
We continued our search for the now seemingly mythical white stripe blackbirds for about three hours before we gave up and walked dejectedly down onto the trail that went around the nearby pond next to Elkhorn Slough. A pectoral sandpiper and several semipalmated plovers foraged in what I thought looked suspiciously like watery decomposing cow manure. A cinnamon teal flew by.
We ran into an older English birder who said he had been coming to Moonglow for years. He said the tricolored blackbirds were molting, which was why the feathers looked yellow instead of white. All the red-winged blackbirds he had seen at Moonglow had been of the California bicolored group, so they had almost no color other than red on their wings. Therefore, they were even easier to distinguish from the tricolored blackbirds than the more eastern group of red-winged blackbirds would be.
The heavens opened and I heard the angelic chorus sing.
We got our life bird tricolored blackbird, but more importantly, I was able to leave feeling that I had learned and now understood the identification of North American Agelaius blackbirds at a deeper level. Clearly, size of the light color on the shoulder is a much better field mark for separating male red-winged and tricolored blackbirds than color. Even if the red-winged blackbirds at that particular location had been of the more eastern “tricolored” group, they still wouldn’t have had as thick a light stripe as the tricolored blackbirds did. We did not escape Moonglow unscathed, however, our rental car — newly christened the Mobile Cow Pie — smelled like a dairy for the rest of our vacation, and when we returned it at the airport it was the dirtiest car in the garage by a large margin. Oh well, some things are worth a little dirt.