Tactics and Vectors analses of data of butterfly migration in southern Ontario Table IX

Tactics and Vectors 98/99

Compass Bearings Hypothesis

Suns' Azimuth Hypothesis

Expansion-Contraction Hypothesis

Never Go Back Hypothesis

Analyses of Pooled Field Data: Hypothesis Testing

Hypothesis Testing: Comparisons of Mean Bearings to theoretical bearings, or theoretical directions, for the pooled data for the 1978, 1979, and 1981 Monarch butterfly (Danaus plexippus) migrations Ś Up Ś Tables: Ś I, II, III, IV, V, VI, VII, VIII a, VIII b, IX, X, XI, XII Ś
Table IX* Hypotheses A: Mean Bearings of migrating D. plexippus cannot be distinguished from the local Great Circle Route to the Overwintering sites in Mexico Hypothesis B: Mean bearings of D. plexippus cannot be distinguished from the bearings for the Kiepenheur and Schmidt-Koenig Magnetoclinic Route
				Mean Bearing ą 95% Confidence Intervals overlap with the:
Sample	Number	Mean Bearing	95% C.I.	Great Circle Route (222°)	Magnetoclinic Route (234°)

Mean Bearing	575	222° (SW)	ą5°	YES	NO
Preferred I	49	232° (SW)	ą16°	YES	YES
Preferred II	24	234° (SW)	ą13°	YES	YES

* Adapted from Gibo, D. L., 1990

Definitions of abbreviations and symbols: N = North, NE = Northeast, E = East, S = South, SW = Southwest, WSW = West-Southwest, etc., C.I. = Confidence Intervals.

Conclusions

Null Hypothesis A cannot be rejected for the Mean Bearing of the Population, nor for the mean bearing of Preferred Direction I, nor for the mean bearing of Preferred Direction II. Migrating D. plexippus in southern Ontario tends to be displaced in approximately the direction of the local Great Circle Route.
Null Hypothesis B is rejected for the Mean Bearing of the Population. The mean direction of displacement of the migrating population is not the direction of the Magnetoclinic Route.
Null Hypothesis B cannot be rejected for either the mean bearing of Preferred Direction I or the mean bearing for Preferred Direction II.

Comments

I would feel better about the apparent match of the Mean Bearing for the population with the theoretical Great Circle Route if I knew that I had an unbiased sample. Unfortunately, it was not possible to make observations every day from from dawn until dark. Instead, I made observations when I had the opportunity and was almost certainly biased towards periods when migration was manifest. Preferred Direction I, and especially, Preferred Direction II are better tests of whether D. plexippus are flying either of the two theoretical routes.
The apparent match for Preferred Direction II with the Kiepenheur and Schmidt-Koenig Magnetoclinic Route should be viewed with caution given that the large 95% Confidence Intervals also include the Great Circle Route. Larger sample sizes are required to narrow the Confidence Intervals (hopefully) before it becomes possible to distinguish between the two theoretical routes.