Dealing With Presence Only Data Create “pseudo-absences” From all of the places a species is not found, randomly select some to act as absences
Problem: False Absences Sampling effort varies Pseudo-absence methods deal with this poorly WE NEED SOMETHING BETTER
Estimating Sampling Effort Repeated visits: can use absences Use reports of other species as estimate of effort?
Data Database of UK butterfly records Use 8 most common species 10km x 10km squares Covariates: proportion of habitat
The Species Images from www.flickr.com Green Veined White Pieris napi Source: oldbilluk /oldbilluk/3504529745/ Red Admiral Vanessa atalanta Source: Durlston Country Park durlston/2891053154/ Large White Pieris brassicae Source: jpockele /jpockele/196916845/ Meadow Brown Maniola jurtina Source: Durlston Country Park durlston/2553616249/ Speckled Wood Pararge aegeria Source: Yersinia yersinia/3465615645/ Small Tortoiseshell Aglais urticae Source: Wanja Krah wanjakrah/4552290666/ Peacock Inachis io Source: Chris@184 chrisbradbury/2745513954/ Small White Pieris rapae Source: MarcelGermain marcelgermain/1935857010/