Can you track the delirious ducks?

ducks.py

import random

DIR_UP = 'u'
DIR_RIGHT = 'r'
DIR_DOWN = 'd'
DIR_LEFT = 'l'

START_POS = (1, 1) #(x_coordinate, y_coordinate)
POND = (3, 3) #(pond_width, pond_height)

def available_moves(pond, duck_pos):
    moves = [DIR_UP, DIR_RIGHT, DIR_DOWN, DIR_LEFT]
    if duck_pos[0] == 0:
        moves.remove(DIR_LEFT)
    if duck_pos[0] == pond[0] - 1:
        moves.remove(DIR_RIGHT)
    if duck_pos[1] == 0:
        moves.remove(DIR_UP)
    if duck_pos[1] == pond[1] - 1:
        moves.remove(DIR_DOWN)
    return moves

    
def move_duck(pond, duck_pos):
    possible_moves = available_moves(POND, duck_pos)
    move = random.choice(possible_moves)
    
    if (move == DIR_UP):
        duck_pos = (duck_pos[0], duck_pos[1] - 1)
    elif (move == DIR_LEFT):
        duck_pos = (duck_pos[0] - 1, duck_pos[1])
    elif (move == DIR_DOWN):
        duck_pos = (duck_pos[0], duck_pos[1] + 1)
    elif (move == DIR_RIGHT):
        duck_pos = (duck_pos[0] + 1, duck_pos[1])
    return duck_pos


def run_simulation(num_ducks):
    ducks = []
    for x in range(num_ducks):
        ducks.append(START_POS)
    
    move_count = 0
    
    while True:
        move_count += 1
        # Update the movement of the ducks
        for i in range(len(ducks)):
            ducks[i] = move_duck(POND, ducks[i])
        # Check to see whether they're all the same value
        if (len(set(ducks)) == 1):
            return move_count

        
def calculate_average(num_ducks=2):
    simulation_count = 1000
    simulation_values = []
    
    for x in range(simulation_count):
        simulation_values.append(run_simulation(num_ducks))
    return sum(simulation_values)/ len(simulation_values)


print("Two ducks in a pond:", calculate_average())
print("Three ducks in a pond:", calculate_average(3))