The Data

Here is an outline of some of the data used to produce the Birds of Northumberland County as well as some reports that summarize the entire data set.

Number of records: 283,823
Number of species represented: 369 (including Brewster's Warbler and Lawrence's Warbler and excluding doubtful accounts)
Year of earliest records: 1813
Date of this snapshot: June 9, 2008

Basic Summary

Report: Basic Summary.

This report lists all species that occur in the data together with their earliest and latest dates, maximum number seen, number of records, and number of years represented in the data. Species with no dated records are not included.

The definitions used in the report are given below.

Earliest Date and Year Gives the date of a sighting for this species closest to January 1. Note that "earliest" is a misleading adjective for those species that arrive in the fall and depart in the spring. Note also that for records with inexact dates the day will be 0 when only a month and year are recorded.

Latest Date and Year Gives the date of a sighting for this species closest to December 31. Note that "latest" is a misleading adjective for those species that arrive in the fall and depart in the spring. Note also that for records with inexact dates the day will be 0 when only a month and year are recorded.

Maximum Number Seen Gives the largest number of individuals recorded in one place at one time. Since summary records are included here, Christmas Bird Counts for example, some caution must be used with this number.

Number of Records Gives the number of records possessing a date in the data set for this species.

Number of Years Gives the number of years that this species has been recorded.

Note Some species are not included in this report because their records lack dates.

Basic Summary - Split Year

Report: Basic Summary - Split

This report is a variant of the Basic Summary and divides the year into two halves: January 1 - June 30, and July 1 - December 31; with dates given for each half. This is to eliminate the problem presented by species wintering in the county, as these would all show arrivals of January 1 and departures of December 31 if the full year alone was used. It also has the potential advantage of showing separate arrivals and departures for spring and fall, although in practice individuals of most passage migrants have lingered over the mid-year break point.

Species By Month and Year From 1975

Report: Number of Species by Month and Year

This table reports the number of species identified in Northumberland County by month and year since 1975. There are some very interesting patterns, not all of which are explained.

There is a definite increase in the number of species reported annually. The high of 281 in 1999 represents a 21% increase over the low of 232 in 1975. Almost certainly much of this has to do with under-reporting in the 1970s and 1980s.
The very low numbers in many months in the 1970s and 1980s are due to under-reporting.
A slow increase throughout the 1990s gives way to a surge in 1999. The reason for this is not apparent yet.
May sees the largest number of northward migrant species.

Number of Records for Each Species By Year From 1975

Report: Records by Species and Year

This table reports the number of records for each species identified in Northumberland County by year since 1975.