Roxburgh local Mykayla Robert alerted Doc to the large number of dead gulls last month, observing there were ``one or two seagulls every metre right along the shore line''.
Five of the carcasses were sent to Massey University to determine the cause of death.
Doc senior ranger, biodiversity (Central Otago), John Keene, said up to 40 black billed gull carcasses were found.
``Test results showed these were straightforward cases of emaciated and starving juveniles.
``The scientists at Massey commented that it seemed the hot, dry weather was taking its toll on many juvenile birds this season.''
During summer, black-billed gulls fed mainly on invertebrates from rivers and pastures, Mr Keene said.
``It is likely that the hot, dry summer led to low river levels, warm river water, and dry pastures, which in turn led to these food sources becoming less available than usual,'' he said.
The weather in the last four months was a problem for many birds around New Zealand, Mr Keene said.
``Although it is sad to lose so many birds, it was simply a bad breeding season and still falls within the normal range for juvenile deaths of black-billed gulls.''
Without knowing for sure, Mr Keen thought it was a ``definite possibility'' that the previous case of mass die-offs in 2012 in the same area was due to the same cause.
