Odd DNS lookups - not sure if there is something wrong with my DNS setup?

[ADB100]

I am trying to understand if I have a problem or not - everything seems to be working OK but I have noticed some odd DNS queries from Windows 7 clients for my 2008R2 Domain. All the DCs are 2008R2 and the domain functional level is 2008R2, all the DCs are also DNS servers and all my zones are stored in AD. All the DNS SRV entries I expect to see are there however if I launch any of the AD management tools on a Windows 7 client I see the client make two DNS lookups for entries that don't exist. So assuming my Domain is 'domain.local' and one of the DCs is called DC1 and the site I have created is called 'SITE1'. When I launch AD Users & Computers I see these two lookups:

_ldap._tcp.SITE1._sites.DC1.domain.local: type SRV, class IN
_ldap._tcp.DC1.domain.local: type SRV, class IN

both of which get a return of 'No such name'

I would only expect the client to lookup

_ldap._tcp.SITE1._sites.domain.local
_ldap._tcp.domain.local

As I say everything seems to be working ok but what I don't understand is why the client is trying to look up these names?

Andy