Friday, July 4, 2008

Bird Survey

Yesterday morning I was able to get out for probably the one bird survey I am going to get done this spring.

I have been establishing a few Breeding Bird Survey style monitoring routes around Valley County in intact prairie habitat to get a better idea of the distribution and relative abundance of bird species in the area. The data collected from these surveys will be fed into the models used to predict distribution in Montana. This survey I did yesterday helped fill in a part of the county where I hadn't established a survey yet.

Valley County has three very distinct major habitat types. The Milk River bisects the county, flowing southeast across the middle of the county to join the Missouri River just below Fort Peck Dam. The river valley habitat is mostly agricultural with large patches of Plains Cottonwood, Green Ash, and Box Elder forests forming the riparian zone along the river. The broad floodplain of the river was formerly large expanse of Silver Sage and probably was a primary wintering area for large numbers of Pronghorn and Greater Sage-Grouse. Most of the Silver Sage has now been converted to irrigated farmland over the last 100 years as a result of increased availability of water in the Milk River from a major diversion of water from the Saint Mary River into the Milk near their headwaters. This major change in the hydrologic cycle of this river has altered the ecology of the river and the associated riparian areas.

North of the Milk River lies a large expanse of glaciated plains. This is the heart of the grassland bird habitat and forms part of one of the largest blocks of remaining intact native northern mixed grasslands left in North America. A good portion of the grasslands in northern Valley County is in public ownership, both BLM and the State of Montana. Much of the remaining land is in ownership of large ranches interested in maintaining grasslands as well and one of them just recently entered into a conservation easement with Montana Fish, Wildlife and Parks to keep it intact. We have had what we hope will be a long term monitoring project for grassland birds going in this landscape for the last 6 years and we feel that we have a pretty good idea of the distribution of birds in this landscape.

Greater Sage-Grouse - I found two broods with at least eight well-grown chicks in each brood.

South of the Milk River is a much different landscape. It is composed of poorer soils and and sparse vegetation dominated by Wyoming Big Sage. This is where some of the best remaining Greater Sage-Grouse populations in North America are found. Which leads us back to the beginning. We haven't been doing the intensive point count surveys in this area like we have done in the northern part so I have initiated a few Breeding Bird Survey style routes on roads through this habitat.
The route I did yesterday took me through part of the area where Mountain Plovers are fairly common and one of the few areas where these birds breed without being associated with prairie dogs. The bentonitic soil in one drainage in particular is not productive for vegetative growth and so it grows Mountain Plovers pretty well. McCown's Longspurs too. This area has been designated a Globally Important Bird Area because of the number of Mountain Plovers found breeding here. I found three Mountain Plovers when I was doing my counts. On my way back to town after getting done with the counts I found another group of 4 with at least four chicks.
Mountain Plover

Mountain Plover

McCown's Longspur

I have found a few Sage Thrashers on my other South Valley County route but none on this one. Perhaps the most interesting and unexpected bird I found this time was a Bobolink. I found one male singing at one of my points and found another on my way back home at the same spot. It was the edge of a reservoir surrounded by sage and rangeland. The rains this spring appeared to have provided enough moisture to fill the reservoir to the point where a good growth of grass occurred along the shallow end of the reservoir. These two birds somehow found this small patch of Bobolink habitat in the sea of sage. I flushed a brood of Greater Sage-Grouse out from underneath the area where the Bobolink was displaying.
One of the most common birds on this route was the Lark Bunting. Pretty much each stop had at least 3 or 4 birds and some had many more than that.

Sage Thrasher


On my way back home I found a Bullsnake on the road. I pulled over to get him off the road so he didn't get run over and he really did not appreciate the attention. This was one of the most aggressive Bullsnakes I have encountered and he did his best to imitate a Rattlesnake by rattling his tail and puffing up and turning sideways. I was finally able to get him to slide backwards and off the road while he was puffed up and striking at me.


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