Earlier Spring Arrival Dates of Migrating Birds Verified in New York and

Massachusetts Christopher Klee and Steven Houck

Le Moyne CollegeDonald McCrimmon, Faculty Mentor

Bird Migration Phenology

• Phenology is a branch of science dealing with the relations between climate and periodic biological phenomena. Such as bird migration or plant flowering.• 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 birds

to migrate northward sooner and arrive earlier.

What is the Evidence for Changes in Temperature?

• The average temperature from January to May in the northeastern US has increased significantly over the past century.

• These data are from Ithaca• Soot and sulfate aerosols are thought to

have reversed the rate of increase from 1940-70, but overall it’s still statistically significant.

• Mathematically, (by finding the second derivative) we can see that the point where temperature really increases is in the year 1950.

Methods

• Our hypothesis is that First Arrival Dates (FADs) are progressively earlier as temperature increased in the 20th and early 21st Centuries• We obtained FADs from Worcester, MA and the Cayuga Lake Basin, NY

from Dr. Chris Butler (Ibis 2003).• These were records from 1932-1993 published in the Forbush Bird Club

journal, The Chickadee.• Cayuga Bird Club records were also digitized by Butler from records extending

back to 1903.

• We then added data from 1994-2013 for both clubs, correcting some previous transcription errors in the Forbush data set.

Methods

Statistical Analysis:• We converted calendar FADs (month, day) to Julian dates (number in a year of

a day and month, e.g. January 1 = 1, December 31 = 365 or 366 in leap years)• We compared average FADs for 28 bird species that Butler (Ibis 2003) had

found to demonstrate earlier arrival dates over multiple decades in both MA and NY.• Over time

• Intervals: 1903-1950, 1951-1993, 1994-2013 – following Butler’s original analyses• By Migration Distance

• Short vs Long

All images from Birds of North America galleries

Results – Earlier Mean (± SD) Dates!03-50 Mean 51-93 Mean 94-13 Mean Total Difference

Cayuga Overall 93.37 ± 23.94 71.58 ± 34.07 59.40 ± 38.87 33.97

Cayuga Short Distance Migrants

95.00 ± 19.13 66.25 ± 33.18 53.82 ± 34.76 41.17

Cayuga Long Distance Migrants

91.19 ± 29.98 78.68 ± 35.37 66.83 ± 44.23 24.36

Forbush Overall 65.70 ± 26.61 49.41 ± 29.22 40.24 ± 33.52 25.46

Forbush Short Distance Migrants

64.22 ± 23.34 45.74 ± 23.68 36.99 ± 30.17 27.23

Forbush Long Distance Migrants

67.68 ± 31.44 54.29 ± 35.85 44.58 ± 36.37 23.10

Results – Cayuga Analysis of Variance

Source Df F value Sig.

Corrected Model 5 3.457 .007

Distance 1 .977 .326

Interval 2 6.881 .002

Distance * Interval 2 .572 .567

Results – Forbush Analysis of Variance

Source Df F value Sig.

Corrected Model 5 2.302 .053

Distance 1 .982 .325

Interval 2 4.971 .009

Distance * Interval 2 .056 .946

Results – Bonferroni Tests Among Interval Means

Cayuga - Interval Significance Forbush - Interval Significance

03-50 vs 51-93 .048 03-50 vs 51-93 .134

03-50 vs 94-13 .001 03-50 vs 94-13 .006

51-93 vs 94-13 .517 51-93 vs 94-13 .765

Discussion• Our results are generally consistent with Butler’s

• Increasingly earlier arrivals in both regions.• Particularly pronounced between the earliest and most recent intervals

• Butler determined the short distance migrants arrived earlier than long distance migrants• Our analysis showed that differences in arrival dates between these groups were not

statistically significant.• This result bears additional follow up• Long distance migrants over wintering in Central and South America should be less influenced by

weather conditions in the north-east US, with no way of directly knowing weather conditions on breeding grounds.

• Some species show evidence of over-wintering (i.e., not migrating).• For example, Yellow-rumped Warbler and Fox Sparrow

• These partial results are preliminary.• 28 of 103 species.

Acknowledgments

• The Members of the Cayuga and Forbush Bird Clubs 1903 - 2014• Dr. Chris Butler• Dr. Charles Smith• Dr. Lawrence Tanner• Fr. George Coyne• Ms. Katheryn Hennigan• Dr. Richard Quimby• Dr. Caitlin Cunningham• Mr. John Livermore