script wont destroy sound at night time?

When it's night, this script is supposed to destroy this sound that is playing in the workspace, but it doesnt. It places the sound in just fine, but wont destroy it. This is really annoying me. Any help?

while true do
    wait()
    if game.Lighting.ClockTime >= 7 and game.Lighting.ClockTime <= 17 then
        if workspace:FindFirstChild("Seagull") == nil then
            local sound = script.Seagull:Clone()
            sound.Parent = workspace
            sound:Play()
        end
    if game.Lighting.ClockTime <= 6 and game.Lighting.ClockTime >= 18 then
        if workspace:FindFirstChild("Seagull") ~= nil then
            workspace.Seagull:Destroy()
            end
        end
    end
end

thanks for reading