Effect of research activity on the success of American robin nests

We investigated researcher effects on the success of American robin (Turdus migratorius) nests from 1993 through 1995 in Ld Plata County, southwest Colorado. We handled the contents of 56 nests in 1993; 33 nests in 1994, and 20 nests in 1995. In these nests, which we refer to as ''touched nests,'' each egg was handled one time, and each chick mas handled for about 3 minutes every 1-3 days. We made no attempt to mask our scent, such as with use Of rubber gloves. With the use of a mirror on an extension pole, we monitored an additional 14 nests in 1993, 12 nests in 1994, and 21 nests in 1995 that we did not touch. Although we monitored nests that we could not reach, in the analyses we included only nests that we could have touched, less than or equal to 3.7 m high. In 1993, a significantly greater proportion of touched nests was successful in fledging at least one robin (57.1%) than untouched nests (21.4%, P < 0.05). Similarly, in 1994, 60.6% of touched nests were successful whereas 8.3% of untouched nests were successful (P < 0.01). In 1995, when we controlled for nest height by touching every other nest that was less than or equal to 3.7 m, success between touched and untouched nests was similar (35.0% for touched nests and 23.8% for untouched nests). Our results strongly suggest that monitoring nests and handling eggs and chicks did not affect negatively the success of American robin nests at our study site.