houck bird migration presentation
TRANSCRIPT
The Effects Of Increasing Temperature On First Arrival Dates Of Migrating Birds In
MassachusettsSteven Houck
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.
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
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)
Turkey Vulture
y = -1.6391x + 3307.7R² = 0.6194
0
50
100
150
200
250
1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 2020
Julia
n A
rriv
al D
ate
Year
Spring Arrival Dates
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
Virginia Rail
y = -1.2586x + 2603.9
0
50
100
150
200
250
1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 2020
Julia
n A
rriv
al D
ate
Year
Spring Arrival Dates
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
Julia
n A
rriv
al D
ate
Year
Spring Arrival Dates
Fox Sparrow
y = -0.3821x + 798.74R² = 0.078
0
10
20
30
40
50
60
70
80
90
100
1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 2020
Julia
n A
rriv
al D
ate
Year
Spring Arrival
Wood Thrush
y = -0.0508x + 219.86R² = 0.0424
0
20
40
60
80
100
120
140
1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 2020
Julia
n A
rriv
al D
ate
Year
Spring Arrival Date
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.
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