Nest Data Quality vs. Time

Reasonably accurate information on nest box productivity is important, especially in new programs or where a proactive resource management approach is desired. Productivity results and nesting behavior can be hard to interpret especially without a good egg membrane count and to a lesser extent, without relatively fresh down and unhatched eggs left in their immediate “post-nest” natural position.

Late winter and early spring inspections often miss or misinterpret the “clues” left behind as residual nest information may change. For example, membranes are eaten by inspects or removed by other nest users, down gets scattered, wet and matted, old eggs break/get broken or substantially altered to mask potential nest strife or predation.

In more than one project area where interim nest inspections were initiated as compared to annual, early spring inspections, MWDI determined that under-counting of duckling production was substantial. Further, nest strife and snake predation, in particular, had not been recognized as problems affecting overall productivity.

In an attempt to document more fully the impact on productivity estimates that the passage of time causes, MWDI established 75 “control” nests in 2006 where nest productivity is confidently known. These nest boxes will be checked again in early spring 2007 and another hatch result will be estimated by a different inspector and the results compared. Unhatched eggs were removed so it will basically be a membrane versus membrane count.

This research will be expanded to encompass assessment of nest strife and other qualitative factors to try and document better the merits of interim and prompt inspections following the nesting season and to help determine where such efforts are not necessary.

For mature nest programs where only one box visit has been made, MWDI encourages sponsors to conduct a nest maintenance inspection in mid-late summer instead of early spring to obtain a reasonably accurate perception of nest results before other events alter the data. Nest materials can be changed then and left for the following spring season. The weather is also nicer and there are more natural things alive to see (and potentially avoid!).

On new programs or in mature programs where actual results are not really known, an interim inspection mid-nest season and then a late summer inspection is strongly encouraged to help establish the overall status of the program. Once this data reference is known, subsequent inspection frequency and timing can be altered down to the individual box in many cases.

However, in MWDI’s brief tenure, there has not been one nest program that has not been favorably enhanced after conducting an interim and then another nest inspection in late summer.