By "blanks" do you mean the periods "." that indicate missing values and are associated with df=0 and Estimate=0?
If so, then those are not indicative of a problem per se (although you do, I believe, have a problem with your model specification, which I'll address below). The short answer is that by default GENMOD includes an intercept and uses GLM (reference-cell) coding where the last level of each factor is the reference. The parameter for the reference level (e.g., habitat 4) is *set to zero*; thus, the parameter estimate has SE=0, and the other statistics fall out accordingly. See the "Parameterization Used in PROC GENMOD" section in the SAS/STAT GENMOD documentation for a wealth of useful details.
However, I think you still have a problem: You have 20 observations. The MODEL statement instructs GENMOD to estimate the following parameters:
1 intercept
3 habitat
4 site
12 habitat*site
--------------------
20 parameters total (as listed in your output)
which leaves you with zero df for any stat tests.
To obtain a significance test of whether means are equal for all levels of some fixed-effects factor (like HABITAT), you need appropriate replications of HABITAT. I might guess that you are thinking of SITEs as replications of HABITAT. If so, then your model statement should look more like
model bats=habitat / dist=poisson type3 scale=deviance;
Something else to think about is whether your count data follow the Poisson distribution well. For the Poisson, the mean is equal to the variance; often counts have variance greater than the mean, which is known as over-dispersion. Sometimes a negative binomial is appropriate. Sometimes the counts are high enough that a normal distribution fits well. Sometimes there are too many zeros ("zero-inflated"). Counts are not always Poisson; you just have to dive in and find out.
HTH,
Susan
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