Observations on the Life History of the Dipper in Montana

Abstract

The general life history of the Dipper (Cinclus mexicanus) was studied on Rattlesnake Creek, Missoula County, Montana. Nestling birds were color-banded, juveniles and adults trapped and marked. When diving Dippers used the wings to a considerable extent. The maximum time spent submerged was between 15 and 20 seconds. The deepest measured dive was four feet. Dippers commonly flew within two or three feet of the water but on longer journeys this was increased to between three and six feet above water. Only on two occasions did a bird fly overland. Dippers appear to feed upon Plecoptera and Ephemeroptera found on the rocks within the stream. Trichoptera larvae, fish fry, and plant food were occasionally eaten. Defecation was frequently caused by the observer's presence and rarely occurred in flight. The frequently heard alarm note was usually elicited by the observer's presence, but was also heard in connection with territorial defense behavior. Singing was strongest from December through early April. No song was heard from June 6 to September 11, 1956. Pairing occurred throughout March. An intensive shaking of wings accompanied by loud singing was perhaps indicative of courtship behavior. Copulation took place from two to four weeks after the birds paired. Chasing appeared to precede copulation. Of eight nests located, two were newly constructed, others were old repaired nests. Some Dippers may return to the same nesting site over a period of several years. Nesting may sometimes begin in late March, and extend into July. Observed clutch size was four to five. The incubation period was 16 days, the nestling period 24 to 25 days. There was no evidence that more than one brood was raised during a breeding season. Fledglings remained around the nesting site from 4 to 14 days. The post-juvenal molt took place within about six weeks after fledgling dispersal