Most
routers don't log what you're doing (which websites you visit etc) - they're not powerful enough to handle that. They just log errors and things of that nature, such as this sampling:
[TABLE="class: formlisting, width: 535"]
[TR]
[TH="bgcolor: #DFDFDF"]Priority[/TH]
[TH="bgcolor: #DFDFDF"]Time[/TH]
[TH="bgcolor: #DFDFDF"]Message[/TH]
[/TR]
[TR]
[TD="bgcolor: #DFDFDF"][INFO][/TD]
[TD="bgcolor: #DFDFDF"]Sun Feb 26 18:57:41 2012[/TD]
[TD="bgcolor: #DFDFDF"]Allowed configuration authentication by IP address 192.168.0.190[/TD]
[/TR]
[TR]
[TD="bgcolor: #DFDFDF"][INFO][/TD]
[TD="bgcolor: #DFDFDF"]Sun Feb 26 17:15:41 2012[/TD]
[TD="bgcolor: #DFDFDF"]Blocked incoming TCP packet from 86.141.111.69:53164 to 10.76.2.252:50992 with unexpected sequence 3649733303 (expected 3648083820 to 3648225260)[/TD]
[/TR]
[TR]
[TD="bgcolor: #DFDFDF"][INFO][/TD]
[TD="bgcolor: #DFDFDF"]Sun Feb 26 17:15:38 2012[/TD]
[TD="bgcolor: #DFDFDF"]Above message repeated 1 times[/TD]
[/TR]
[TR]
[TD="bgcolor: #DFDFDF"][WARN][/TD]
[TD="bgcolor: #DFDFDF"]Sun Feb 26 16:04:31 2012[/TD]
[TD="bgcolor: #DFDFDF"]A network computer (xxxxxxx) was assigned the IP address of 192.168.0.199.[/TD]
[/TR]
[TR]
[TD="bgcolor: #DFDFDF"][INFO][/TD]
[TD="bgcolor: #DFDFDF"]Sun Feb 26 16:04:31 2012[/TD]
[TD="bgcolor: #DFDFDF"]Wireless system with
MAC address xxxxxxx associated[/TD]
[/TR]
[TR]
[TD="bgcolor: #DFDFDF"][INFO][/TD]
[TD="bgcolor: #DFDFDF"]Sun Feb 26 16:04:25 2012[/TD]
[TD="bgcolor: #DFDFDF"]Wireless system with MAC address xxxxxxx disconnected for reason: Received Deauthentication.[/TD]
[/TR]
[TR]
[TD="bgcolor: #DFDFDF"][INFO][/TD]
[TD="bgcolor: #DFDFDF"]Sun Feb 26 16:04:16 2012[/TD]
[TD="bgcolor: #DFDFDF"]Blocked incoming TCP packet from 193.109.81.88:443 to 10.76.2.252:50412 with unexpected sequence 3186526437 (expected 1332439278 to 1332570349)[/TD]
[/TR]
[TR]
[TD="bgcolor: #DFDFDF"][INFO][/TD]
[TD="bgcolor: #DFDFDF"]Sun Feb 26 16:04:13 2012[/TD]
[TD="bgcolor: #DFDFDF"]Above message repeated 1 times[/TD]
[/TR]
[TR]
[TD="bgcolor: #DFDFDF"][INFO][/TD]
[TD="bgcolor: #DFDFDF"]Sun Feb 26 16:03:16 2012[/TD]
[TD="bgcolor: #DFDFDF"]Blocked incoming TCP packet from 93.186.25.40:443 to 10.76.2.252:61808 with unexpected sequence 862731828 (expected 1557427061 to 1557558132)[/TD]
[/TR]
[TR]
[TD="bgcolor: #DFDFDF"][INFO][/TD]
[TD="bgcolor: #DFDFDF"]Sun Feb 26 16:03:13 2012[/TD]
[TD="bgcolor: #DFDFDF"]Above message repeated 1 times[/TD]
[/TR]
[/TABLE]
However, tools such as Wireshark are designed to actively sniff the network to see exactly what you're up to. If he really wants to pore over huge amounts of data or is looking for something specific, that is.