Dear all,

I am trying to fit a set of models with lmer function.
My aim is to investigate the relationship between the abundance of a mammal
species (count) and several environmental variables.
The sample size is 648, but the observations are not independent and the
random effect is nested: I have 10 study areas, within each area I
performed 6 transects. I have 9-10 observations in all transects. So an
example of a model with a single independent variable is:
mod05<-lmer(cagaders~E_arb_alt+(1|ter)+(1|ter:trans),data=conill,family=poisson)

When running this model I get the warning:
In mer_finalize(ans) : singular convergence (7)


I don't see an apparent reason for this warning.
I would be very grateful if someone can help me to solve this problem and
to know wether the results in the fitted model are credible.

Thank you very much in advance,

Toni

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Antonio Hernandez Matias

Departament de Biologia Animal (Vertebrats)
Facultat de Biologia
Universitat de Barcelona
Av. Diagonal, 645
Barcelona      08028
Spain
Telephone: +34-934035857
FAX: +34-934035740
e-mail: ahernandezmatias@ub.edu

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