1. The Effects Of Increasing
Temperature On First Arrival
Dates Of Migrating Birds In
Massachusetts
Steven Houck

2. Why Study Bird Migration?
• Many species of birds leave the northeastern states to winter in
places where food is abundant.
• They return in the spring, when food again becomes available to feed
their young.
• If the environment has grown warmer over the decades, we might expect
them to migrate northward sooner and arrive earlier.

3. What is the Evidence for Changes in Temperature?
• The average temperature from
February to May in the
northeastern US has increased
significantly over the past century.
• Soot and sulfate aerosols are
thought to have reversed the rate
of increase from 1940-70, but
overall it’s still statistically
significant.
• The question is: has even this kind
of environmental change affected
bird behavior?
National Weather Records Center data

4. Method
• I obtained data from Worcester, MA from Dr. Chris Butler.
• These were records of First Arrival Dates (FAD) from 1932-1993 in the Forbush Bird
Club journal, The Chickadee.
• I then added data from 1994-2012 and corrected some previous
transcription errors.
• A data set spanning 70 years!
• Statistical analysis:
• I converted calendar FADs (Month, day) to Julian dates (the number in a year of a day
and month, e.g., January 1 = Number 1, December 31 = Number 365.
• I conducted regression analyses between FADs and Years and fitted linear trends for
the entire 1932 – 2012 time series.
• Because the distributions were non-normal I then used Kruskal-Wallis ANOVA
followed by Tukey HSD post-hoc comparisons of selected time intervals.
• Group A (1932-1950), Group B (1951-1993), Group C (1994-2012)

5. Turkey Vulture
y = -1.6391x + 3307.7
R² = 0.6194
0
50
100
150
200
250
1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 2020
JulianArrivalDate
Year
Spring Arrival Dates

6. Blue-winged Teal
y = -0.207x + 502.04
0
20
40
60
80
100
120
140
160
1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 2020
Spring Arrival Dates

7. Virginia Rail
y = -1.2586x + 2603.9
0
50
100
150
200
250
1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 2020
JulianArrivalDate
Year
Spring Arrival Dates

8. Yellow-rumped Warbler
y = -0.7818x + 1600.4
0
20
40
60
80
100
120
140
1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 2020
JulianArrivalDate
Year
Spring Arrival Dates

9. Fox Sparrow
y = -0.3821x + 798.74
R² = 0.078
0
10
20
30
40
50
60
70
80
90
100
1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 2020
JulianArrivalDate
Year
Spring Arrival

10. Wood Thrush
y = -0.0508x + 219.86
R² = 0.0424
0
20
40
60
80
100
120
140
1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 2020
JulianArrivalDate
Year
Spring Arrival Date

11. Discussion
• Some species show consistently earlier arrival dates.
• (Turkey Vulture, Blue-winged Teal, Wood Thrush).
• Other species show evidence of over-wintering (i.e., not migrating).
• Most pronounced in Yellow-rumped Warbler and Fox Sparrow
• Turkey Vulture and Virginia Rail show over-wintering in more recent years (post
1993).
• Possible contributing environmental factors.
• Increase in spring temperatures over entire study period experienced by all
species.
• Food availability for over-wintering species.
• These results are preliminary and partial.
• 6 of 151 species – To be continued.

12. Acknowledgments
• The Members of the Forbush Bird Club 1932 - 2014
• Dr. Chris Butler
• Dr. Charles Smith
• Dr. Lawrence Tanner
• Fr. George Coyne
• Ms. Katheryn Hennigan
• Dr. Richard Quimby
• Dr. Donald McCrimmon