[R-sig-ME] Poisson GLMM: where is the deviance?

[Luciano La Sala]

Dear R experts:

I need to fit the following GLMM with Poisson distribution: glmer(yobs~year
+ (year|stake), data=mibase,family=poisson)


Where "stake" (plots where the number of birds is measured) is as random
effect, and "yobs" is the abundance of birds. I need an estimation of slope
an intercept for the random term.

I specified my model as follows:

glmer(yobs~year + (year|stake), data=mibase,family=poisson)

and I get the following (it does not calculate the deviance)

  Generalized linear mixed model fit by the Laplace approximation

  Formula: yobs ~ year + (year | stake)
     Data: mibase
   AIC BIC logLik deviance
   NaN NaN    NaN      NaN

  Random effects:
   Groups Name        Variance   Std.Dev.   Corr
   stake  (Intercept) 1.4165e-01 0.37636766
          year        3.5469e-08 0.00018833 0.000
  Number of obs: 1186, groups: stake, 63
  Fixed effects:
                Estimate Std. Error z value Pr(>|z|)
  (Intercept)  3.213e+01  6.445e+08       0        1
  year        -1.952e-01  3.225e+05       0        1

- Ignored:

  Correlation of Fixed Effects:
       (Intr)
  year -1.000
  Mensajes de aviso perdidos
  In mer_finalize(ans) : singular convergence (7)


Q. What does this error mean and how can I solve it?

By the way, if I run the same model but only estimating the intercept of
random effects as
glmer(yobs~year + (1|stake), data=mibase,family=poisson) it seems to work
properly.


I look forward for your response and thanks in advance.

Luciana