ML643862079

观察细节

****High Count- I counted them by 1s and marked them in my notebook as I birded the area. Exact count. Upon planning for this trip in western Iowa, I had four mornings to go out in search of sparrows. The weather seemed perfect on 10/18, so I decided to go to this location on this morning. The wind forecast showed completely still conditions in the morning switching to 15-25mph winds in the afternoon, an unusual setup. The temperature on this morning was also colder than previous recent mornings, so I knew that some sparrow migrants could arrive overnight with the still conditions. When I arrived at the wetland this morning, I noticed that the huge tract of prairie land to the east of the canal and north of 250th had been plowed for farming this year, which was very depressing. To add insult to injury, the canal itself was in the process of being scraped clean of its vegetation. The process was started at 250th and went northward but the work was not complete yet. Still, obviously, I was there to see sparrows, so I set out on the west side of the canal, starting at 250th Street. Immediately, I noticed that this was no ordinary day. The sparrow activity was spectacular. I could just stand on the edge of the habitat, and the birds were hopping out to greet me. Another immediate observation was that the Lincoln's Sparrow was dominating these flocks numerically. This is not typical of this usually less numerous species. I knew my goal for the morning. It was to form a route that concentrated on finding the maximum Lincoln's Sparrows in the area. I worked my way along the west side of the canal where the habitat was at its best and the sparrow activity was at its greatest. I would walk further west in sections but generally northward along the canal, not repeating any of the areas observed. The sparrow activity was insane. I looked through my binoculars and through my scope in order to scan all of the birds in view. For the first three hours, the sparrows were so curious and active that all I had to do was walk next to them and they all came out of hiding. After that the activity dropped slightly, and I had to "pish" the sparrows out into view. Even as the wind was starting to pick up around noon, the sparrows would still come into view with "pishing". When I finally left the area hours later, the sparrow activity had dropped to near zero. What are the factors that led to the massive numbers of Lincoln's Sparrows in the area? I think they were multiple. This is the best time of year for sparrows, but daily conditions are critical. The sparrow activity on this morning was at its maximum; they could not have been more active. The habitat was a major factor. I believe the area of the Nolan Wetland to be one of the best sparrow migration areas in this part of the state (based on my own observations and viewing ebird reports), and likely one of the best locations regionally. I also believe that these sparrows were pushed to the west side of the canal by the destruction of the habitat on the banks of the canal. On prior visits to this area, the slopes of the canal contained some of the highest concentrations of sparrows, and when I birded the sides of the canal further north, I found this to still be the case. I also think that this must have been a "stacking" event for the Lincoln's Sparrow. New migrants of this species probably recently arrived and added to the birds that were already using this stopover migration place. It would account for why the Lincoln's Sparrow was by far the most numerous species today. I chase sparrow migration and have a passion for it as much as one would have a passion for hawk migration. The Missouri River valley is one of the most significant migration corridors for sparrows in the country. Most of the habitat in this section of the river lies in Iowa. The wetlands in this section of the sparrow migration corridor are critical for the birds. The sparrows are funneled here from a large area to the north and west. They utilize these prairies as stopover resting points, much like shorebirds in migration. I am always trying to find large numbers of sparrows in October here. This count of Lincoln's Sparrows represents my most significant sparrow count ever. It is a species that is often overlooked but is beautiful and endearing in its own way. Because this concentration of Lincoln's Sparrows of this magnitude is so rare in this section of the country, I would quantify this as the most incredible migration event and count of any species that I have witnessed in my 20 years of birding.