Here is my simple C++ solution,

int migratoryBirds(vector arr) {

int cnt = 0;
int prevCnt = 0;
int res  = 0;
for( int i =1; i <=5; i++)  // if you read the constraint it says only 1 - 5 types guranteed, so we find the max of each element and the corresponding min
{
    cnt = std::count (arr.begin(), arr.end(), i);

    if( prevCnt < cnt )
    {
        prevCnt = cnt;
        res = i;
    }
    else if( prevCnt == cnt )
    {
        res = min(res, i); // here we get the min of the max cnt if they are the same
    }
}
return res;   

}