Link to short story that JKR wrote for charity is n...

[sistermagpie]

 > Alla;
> > 
> > Agreed, and the expression that you were looking for, James and 
> Sirius 
> > are portrayed "alert as gundogs", which to me also suggest that 
> they 
> > see real bad guys. IMO of course.
> 
> Zara:
> Surely, James occasionally looked alert, even, very alert, 
or "alert 
> as a gundog" during Quidditch games? Heck, Sirius managed to look 
> alert in a doglike way when James spotted Sev sitting in the bushes 
> with his nose in a test paper a year or so before this story is 
> supposed to be set. All I get from that is that the people on 
brooms 
> were more of a threat than the fat cop it was funny to irritate.

Magpie:
Yup, that was the line I remembered and I still get the impression 
they're DEs. I think the idea here is that James and Sirius are being 
dashing and heroic and heroic. Not knocking out poor people from the 
Ministry (since when they do show up in person when somebody's even 
doing magic, much less flying a motorcycle), which seems far too much 
overkill to me. I think we're supposed to see the difference between 
the way they can joke around but are still alert as gundogs when a 
threat appears.

James did have a similar expression when going after Snape. Snape was 
up to his eyeballs in the Dark Arts and, perhaps more important, he 
was prey. All these things give me the impression these are too OotP 
boys on the job. And also, most obviously, it's the stronger choice. 
This is the type of scene, imo, where JKR wouldn't pull her punches 
and use Ministry employees checking for magical use in front of 
Muggles when she could use DEs--or if not DEs, at least general bad 
guys. Ministry employees who work in Arthur's department imo aren't 
significantly more of a threat when you're James and Sirius.

-m