NASM 32-bit: printing content of register by printf

I'm new to assembly. I'm having different output for following simple code from what I expected. each time before printf is called, content of eax is shifted to the right by some number. What am I doing wrong? Thanks.

Code:

;file name : testing.asm
;assemble and link with:
;nasm -f elf testing.asm && gcc -m32 -o testing testing.o
extern  printf      ; the C function, to be called

SECTION .data       ; Data section, initialized variables

    a:  dd  15  ; int a=5;
    str:    db "content in eax=%d", 10, 0 

SECTION .text       ; Code section.

    global main     ; the standard gcc entry point
main:               ; the program label for the entry point
    mov     ebp, esp
    mov     eax, [a]    ; put a from store into register

    shr     eax, 1      ; eax content should be 15>>1 = 7
    push    eax     
    push    dword str   ; string to be printed
    call    printf      ; printf(str,content_of_eax)

    shr     eax, 2
    push    eax         ; eax content should be 7>>2 = 1
    push    dword str   
    call    printf      ; printf(str,content_of_eax)    

    shr     eax, 1  
    push    eax         ; eax content should be 1>>1 = 0
    push    dword str   
    call    printf      ; printf(str,content_of_eax)

    mov     esp, ebp    ; takedown stack frame
    mov     eax, 0      ; normal, no error, return value
    ret                 ; return

Output:

content in eax=7
content in eax=4
content in eax=8

Expected Output:

content in eax=7
content in eax=1
content in eax=0