TikZ-picture: remove arrows at starting point of edge

Question

I'm a litte confused, because I drew a TikZ-picture and didn't get what I expected. Have look at the following:

\documentclass[12pt,a4paper]{article}
\usepackage{amsmath, amssymb, ngerman}
\usepackage[latin1]{inputenc}

\begin{document}
\usepackage{pgf,tikz}
\usetikzlibrary{arrows}
\begin{tikzpicture}[line cap=round,line join=round,>=triangle 45,x=0.8cm,y=0.8cm]
\draw[->,color=black] (-3.17,0) -- (5.5,0);
\foreach \x in {-3,-2,-1,1,2,3,4,5}
\draw[shift={(\x,0)},color=black] (0pt,2pt) -- (0pt,-2pt) node[below] {\footnotesize $\x$};
\draw[->,color=black] (0,-3.22) -- (0,7.5); \foreach \y in {-3,-2,-1,1,2,3,4,5,6,7}
\draw[shift={(0,\y)},color=black] (2pt,0pt) -- (-2pt,0pt) node[left] {\footnotesize $\y$};
\draw[color=black] (0pt,-10pt) node[right] {\footnotesize $0$};
\clip(-3.17,-3.22) rectangle (5.35,7.26);
\draw (0,0) rectangle (1,1);
\draw (-1,0) rectangle (0,1);
\draw (0,-1) rectangle (1,-2);
\draw (3,0) rectangle (4,1);
\draw (0,4) rectangle (1,5);
\draw[->] (1,1) edge [bend right] node[above right] {$d_{A,P_1}$} (-1,1);
\draw[->] (-1,0) edge [bend right] node[left] {$d_{A,P_2}$} (0,-2);
\draw[->] (1,-2) edge [bend right] node[below right] {$d_{A,P_3}$} (4,0);
\draw[->] (4,1) edge [bend right] node[above right] {$d_{A,P_4}$} (1,5);
\end{tikzpicture}

\end{document}

I drew some bended edges, but the little arrows showing up at the starting point of my edge are not intended. I have no idea how to fix it but it has something to do with "edge".

Perhaps someone can help me out? Thanks in advance.