The Application Guide only talks about the birth certificate of the primary/main applicant. For dependents, you just need to provide a copy of their passport bio and personal information pages. You can refer to section 3.6 in the Application Guide.
But there is no harm in providing an additional document as the Application Guide itself says 'Officers assessing the application may request additional documents that are not listed among the supporting documents below if they deem that these documents are necessary to assess the application. Failure to provide the additional documents in the timelines requested by the officers will result in the denial of the application.' If you have not provided it, you can keep it ready for future submission, if requested.
