Push Back with Copy Builder

I do not understand why when I create a copy constructor and push it back into a vector, it calls the constructor more than once!

If I only do 1 push back, it will show the copy builder 1 time. if I do 2 push back it increases to 3.

I would also like to know why I can not use & in the builder! foo (foo & p) {}

#include <iostream>
#include <vector>

using namespace std;

class foo {
public :

foo(const foo& p){

    cout<<"Construtor de Copia"<<endl;
    }

    foo () {
    cout << "Chamando o Construtor " << endl ;
    }

    ~ foo () {
    cout << "Chamando o Destrutor " << endl ;
    }
};

int main ( int argc , const char * argv []) {

    vector < foo > v3 ;

    foo f1;

    v3.push_back(f1);
    v3.push_back(f1);


    return 0;
}