Infrequently Asked Questions

If you have questions about the count not addressed in the How to pages, let your compilers know and we will publish them here.

Q. I heard a bird, but did not see it. Does it count?
A. Yes, the NAS Compilers’ Manual states that birds may be identified by voice.

Q. I found a dead bird on CBC day. May I include it in my tally?
A. Yes, but your specimen must be recorded on your checklist as a Count Week bird.

Q. I identified bird tracks on the CBC. Do they count?
A. Tracks should be entered as CW on your checklist unless you can confirm they were not present earlier in the day. Keep in mind that specimens and tracks located during Count Week should not be considered.

Q. I encountered a huge roost of crows. After the roost disperses, how should I account for crows found during the later daylight hours?
A. The Compilers’ Manual states: “For counts where large roosts are within the circle, an observer experienced with estimating large numbers of birds should census that roost in the morning or evening. With very few exceptions, no other individuals of that species counted by other observers during the day should be included in the final tally.”

Q. What is Effort and why do we collect effort data?
A. Our data are “effort adjusted” to make the results more scientifically useful. Over the years the number and birding skills of CBC participants have increased dramatically. Simply stated, we have more volunteers counting birds every year such that the tallies of some bird species have increased independently of any actual fluctuations in their populations. The counts are adjusted using algorithms that “normalize” the data to account for changes in participation rate, miles covered, and hours spent afield from year to year.

In 2003 the CBC protocol was reviewed by an international panel of survey experts and changes to our sampling methods were proposed to reduce bias and create a data set that would be more useful to scientists. Our current effort forms embody many of the ideas set forth by the panel.

The report, titled Improving the Christmas Bird Count: Report of a Review Panel, is here.


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