October 1901. Proceedings of the Nebraska Ornithologists' Union 2: 42-44.
Notes on the Breeding of the Prothonotary Warbler
M.A. Carriker, Jr., Nebraska City
A mile southeast of Hamburg, Iowa, the Nishnabotna River breaks through the chain of bluffs which skirt the Missouri River on the east side, and before the advent of the Chicago, Burlington & Quincy Railway, wound along down the bottom for about thirty miles, finally emptying into the Missouri River ten miles due south of Rockport, Missouri. It gave the railroad company so much trouble by washing out their track that they finally cut a new channel direct to the river, so that it now empties into the Missouri River a short distance above Peru, Nebraska. This left about twenty-five miles of the old bed of the river filled with water and in communication with the Missouri. Its mouth has gradually filled up until now the Missouri has access only during high water. As a result this forms one of the best natural fishing resorts for many miles around, being richly stocked with croppie, perch, buffalo, German carp, sunfish and bullhead. The channel has gradually grown wider until many of the willows lining its banks are now decaying stubs, standing in the water, and forming nesting sites for numerous chickadees, flickers, red-headed, hairy, and downy woodpeckers.
With the many deserted holes for nesting sites and the thick groves of cottonwood, elm, maple and willow trees lining the banks, for feeding grounds, we have a perfect summer haunt for one of the most beautiful and interesting warblers, the Prothonotary. It arrives as near as I can tell about the last week in April, but being in that locality only at infrequent intervals, I have no knowledge as to the exact time when nest building begins, how long a time the bird consumes in this work, etc. That the birds do not all deposit eggs at the same time is evident from the fact that nearly fresh eggs and young of various ages were found on the same day.
For two seasons I had noticed the birds in that locality and in the spring of 1900 I resolved to locate a nest if possible. With this end in view I went down as soon as school closed at the State University.
The second day after my arrival, June 5, while sitting on the bank of the stream idly watching my float, a Prothonotary Warbler alighted on a stub standing in the water about twenty feet from the bank where I sat. I was all attention in a second, and as it clung for a moment to the edge of an old hole in the stub, I saw that it held a worm in its bill. Then the slender bill of the female appeared at the opening, followed by the beautiful golden head. After uttering a few purring notes the male gently put the worm in its mate's mouth and then flew to the grove on the opposite side of the stream, into which it disappeared. Keeping myself well hidden I watched for perhaps twenty minutes, during which time the male came four times with a worm for the incubating female. When I approached the nest, the female flushed as the boat grazed~the stub. She flew into the grove opposite and I did not see her again until an hour afterward as I was passing, when both birds were clinging to the stub, but flew away at the approach of the boat. The large nest cavity was half filled with twigs and decaying shreds of bark and leaves, while the top of the mass was hollowed out and lined with fine bark shreds to form a receptacle for the eggs. Owing to the feet that the stub stood in the water and the nest was only a short distance above it, the nest materials were quite damp and much decayed. The nest contained six almost fresh eggs with a pure white ground color and profusely spotted and specked with reddish lilac. The eggs measure, respectively, .70x.55; .75x.57; .74x.57; .73x.56; .78x.56. Farther down stream two nests were located by watching the birds as they carried food to the occupants, which in these cases proved to be young birds instead of the incubating female as in the first instance. These nests were in stubs standing in deep water but the holes were six and eight feet respectively above its surface. I did not ascertain the number of young in the nests, not wishing to break open the holes and expose the young.
One thing about the action of the parent birds was strange to me and wholly different from anything I had ever noticed before in regard to the actions of warblers when their young were disturbed or in danger. If one of the birds happened to be present when the nest was disturbed or even approached, it merely flew away without any of the usual manifestations of alarm so common among birds and did not return until the intruder had disappeared. As a general rule the birds are shy, occasionally appearing singly on the outskirts of a grove and before you are fully aware of its presence, it has flashed away through the trees like a sunbeam. Again you will be startled by a little burst of song from a thicket close by; but you will have to look closely and with great care before you are able to detect its author as he sways on a slender limb near the ground. The song consists of a series of single syllables, delivered in rapid succession, starting in loud and clear, but gradually running together towards the end and much resembling tsweet, tsweet, sweet-sweet-sweet.
Their food seems to consist largely of caterpillars, which they must get almost exclusively from the trees, since they are very seldom seen feeding on the ground. As long as food is plentiful and the weather favorable they remain with us, but gradually drift southward when conditions are unfavorable. My last trip to their locality was made September 3, when I saw several birds. How long they remained after this I do not know. Careful observation will yield much that is interesting concerning this bird. As far as I have observed its nesting habits here, they agree quite closely with those described for the species on the Illinois River, Illinois, as published by W.E. Loucks. It has been found breeding near Omaha and on both sides of the Missouri River as far north as the middle of the state, but never so commonly as in the locality which I have described.