# ANOVA using day numbers

I am looking at differences in dates of maximum counts of geese at 3 sites in the UK.

My data look like these created in R:

df <- data.frame(day.number=c(sample(70:75, 30, replace=T),
sample(77:82, 30, replace=T),
sample(80:84, 30, replace=T)),
site=paste0('site', sort(rep(1:3, 30))))


The variable day.number is the day number on which the maximum count of geese was recorded in each year. So day number 70 would be 70 days from 1st January in that year. Each row represents a year and there are 30 years worth of data from each site.

I am considering carrying out an ANOVA to test to see if the date of the maximum count is different among sites. Example R code:

summary(aov(day.number ~ site, data=df))


Is an ANOVA appropriate here? Is there a better way of looking at differences in day number of maximum count among sites?