C++ thread issue with data copy

I am trying a simple thread program on using gcc HEAD 7.0.0 20161020 and c+1z(GNU)

Very simple program,

#include <thread>
#include <iostream>

class Task
{
    public:
    Task(int i):_i(i){}
    Task(const Task& p):_i(p._i){std::cout<<"Copy called:"<<_i<<std::endl;}
    void operator()(){std::cout<<"operator()"<<_i<<std::endl;}
    void runTask(void* p)
    {
        if (p) {}
        std::cout<<"runTask():"<<_i<<std::endl;
    }
    private:
    int _i;
};

int main()
{
    std::cout<<"Begin main()"<<std::endl;
    Task tsk1(11);
    Task tsk2(22);    
    Task tsk3(33);    
    std::cout<<"Create threads"<<std::endl;
    std::thread t1 {tsk1};
    std::thread t2(&Task::runTask, &tsk2, nullptr);
    std::thread t3(&Task::runTask, &tsk3, nullptr);

    t1.join();
    t2.join();
    t3.join();

    std::cout<<"End main()"<<std::endl;
    return 0;
}

Which gives output as:-

Begin main()
Create threads
Copy called:11
Copy called:11
operator()11
runTask():22
runTask():33
End main()
0

Can anyone suggest why Copy is created for single object whereas I am passing 2 different this pointers ?