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

Tactics and Vectors 98/99

Compass Bearings Hypothesis

Suns' Azimuth Hypothesis

Expansion-Contraction Hypothesis

Never Go Back Hypothesis

Analyses of Pooled Field Data: Descriptive Statistics

Descriptive statistics for pooled directional data for 1978, 1979, and 1981 Monarch butterfly (Danaus plexippus) migrations in Southern Ontario Ś Up Ś Tables: Ś I, II, III, IV, V, VI, VII, VIII a, VIII b, IX, X, XI, XII Ś
Table V* Proportion of migrating Danaus plexippus flying at low (less than 3 m), intermediate (3 m to 29 m), and high (30 m and above) altitudes for eight wind conditions Directional data were grouped according altitude category and wind direction at the time of the observation.
		*Number and percentage of migrating D. plexippus* in each altitude category for each wind condition**
Wind	N	Alt. < = 3 m	3 m < Alt. < 30 m	Alt. = > 30 m

		Num. %	Num. %	Num. %

North	53	2 3.8	26 49.1	25 47.2
Northeast	64	7 10.9	21 32.8	36 56.3
East	150	13 8.7	39 26.0	98 65.3
Southeast	131	8 6.1	72 55.0	51 38.9
South	15	8 53.3	5 33.3	2 13..3
Southwest	35	6 17.1	12 34.3	17 48.6
West	20	4 20.0	10 50.0	6 30.0
Northwest	107	3 2.8	35 32.7	69 64.5
Population	575	51 8.9	220 38.3	304 52.9

* Adapted from Gibo, D. L. 1986, 1990

Definitions of abbreviations and symbols: N = number in sample, Num. = number in altitude category.

Comments

Although only about 9% of the population was observed flying within 3 m of the ground, more that half of the migrants flying in South winds were within 3 m of the ground. A South wind is a combination of a headwind and a left crosswind to a Southwest course.
The butterflies seldom migratated during periods of Southwest winds, a direct headwind condition. Most of the observations for the SW wind category were made during one morning when mean wind velocity at 1.5 m was only 0.8 m/s.