Using sudo
I think you need to find out what interface is being used for your network and then just tell tshark about it.
Example
Network devices present on my box.
$ ip addr|grep '^[0-9]'|awk '{print $2}'
lo:
eth0:
wlan0:
Run tshark:
$ sudo tshark -i wlan0 | head -5
..start seeing output from tshark...
Using capabilities
The Amazon AMI instances are based on CentOS so you may be able to use the following steps to accomplish what you're after.
$ sudo groupadd wireshark
$ sudo usermod -a -G wireshark saml
$ setcap cap_net_raw,cap_net_admin=eip /usr/sbin/dumpcap
The above creates the Unix group wireshark, adds the user saml to it, and then adds the capabilities using the tool setcap to allow others access to the dumpcap file.
Example
$ tshark -i wlan0
Capturing on wlan0
0.000000 108.160.163.38 -> 192.168.1.20 HTTP HTTP/1.1 200 OK (text/plain)
0.087199 108.160.163.38 -> 192.168.1.20 TCP http > 38987 [ACK] Seq=180 Ack=352 Win=83 Len=0 TSV=144745749 TSER=195830096
0.253077 192.168.1.20 -> 255.255.255.255 DB-LSP-DISC Dropbox LAN sync Discovery Protocol
0.253360 192.168.1.20 -> 192.168.1.255 DB-LSP-DISC Dropbox LAN sync Discovery Protocol
0.779785 192.168.1.20 -> 74.125.225.115 HTTP HEAD / HTTP/1.1
...
You can read more about Linux' capabilities facility via the man pages, man capabilities.
References