First one is an official received in 2013, showing the Great Dune. Nida is located on the Curonian Spit between the Curonian Lagoon and the Baltic Sea, and is the westernmost point of Lithuania and the Baltic states
the stamp is from a set of two Lithuanian Red Book stamps issued in 2013, showing birds. On this one you can see the Tawny Pipit.
I received this second card also in 2013 as part of the Choose a Country RR. This reminds me that I haven't taken part in a RR in ages and it seems it's gonna stay that way for a while =/ Mainly cos of financial reasons, plus my general procrastinating habit, so I believe it aint fair to be engaging in activities that I cannot respond to properly.
Anyways...the card shows the Grabštas cape, that's also part of the Curonian Spit.
the stamp is from a set of two issued in 2009, portraying the Preserve the Polar Regions and Glaciers subject.