DISPLACEMENT OF MIGRATORY BIRDS
Abstract
OBSERVATIONS MAKE IT EVIDENT THAT THE ABILITY TO HOME-NAVIGATE IS NOT POSSESSED EQUALLY BY BIRDS OF DIFFERENT RACES IN THE SAME SPECIES. It also seems likely that birds require some months to become imprinted with a winter home, and that displacement before ''some months'' may result in a new winter-home. Whether these young birds will return to their ancestral breeding place, or adopt a new breeding ground (as do certain European passerines) is not known. Work in our laboratories (on other projects) provides increasing evidence that Zonotrichia use visual means to interpret the night celestial pattern to orient their night restlessness. IT SEEMS NOT UNREASONABLE THAT THE NIGHT SKY MAY BE SUFFICIENTLY FAMILOGICAL CHRONOMETER PERMTS ITS USE FOR A RETURN TO PROPER LONGITUDE IN THIS CASE. The time tken to return from such a distance (e.g., 14 Apr to 24 June for 1800+ miles) would demand a precision chronometer we have not yet seen demonstrated in birds. Perhaps these birds determine the azimuth of home early in their dsplacement and this azimuth is thar to these birds that they use it for return to the home station from distant points. It does not seem that our present concept of a physiological chronometer permts its use for a return to proper longitude in this case. The time tken to return from such a distance (e.g., 14 Apr to 24 June for 1800+ miles) would demand a precision chronometer we have not yet seen demonstrated in birds. Perhaps these birds determine the azimuth of home early in their dsplacement and this azimuth is then ''remembered'' for the weeks necessary to accomplish the return. Should this be so, a reset chronometer would prevent their return from a displacement in longitude. This can be tested. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 26, 1962
- Accession Number
- AD0292799
Entities
People
- L. Richard Mewaldt
Organizations
- San José State University