Annual Nammazhwar Moksham at Srirangam and Garuda Sevai at Nava Tirupati temples, TN are meant to honor the great saint

 The Garuda sevai festival in Nava Tirupathi, the nine Vishnu temples in Thoothukudi region, particularly at  at  Thirukollur Vaithamanidhi Perumal  and the Araiyar Sevai  (recitation of Thiruvaimozhi) during the Vaikunta Ekadasi festival in Srirangam temple are dedicated to Tamil vaishnava saint Nammazhwar. The His pasurams and other azhwars  are reverberated as  part of daily prayers and during festive occasions in most Vishnu temples in South India.

Garuda Sevai in Thirukkoluren.wikipedia.org

Nammazhwar is regarded as the one of the top three Hindu mystics in India, with the other two being Manickavasagar and Kabir. He  is considered  the greatest among the twelve azhwars and  his contributions of  1352  devotional hymns in glory of God Vishnu among the 4000 stanzas in the Nalayira Divya Prabandam bear testimony to his intellectual capacity, spiritual moorings  and hid depth of knowledge in Vaishnavism. In the realm of Vaishnava religious literature, he has reached the dizzy height which other saints can't think of. 

The spectacular Garuda Sevai utsavam (festival) in the month of Vaikasi (May-Jun) witnesses nine Garudasevai, an event in which festival image idols from the nava tirupathis temples namely, Mayakoothar Temple, Makara Nedunkuzhai Kannan Temple, Rettai Tirupathi - South Temple, Rettai Tirupathi North Temple, Vaithamanidhi Perumal Temple, Adhinaatha Perumal Temple - Thirukkurugur, Kaaisinavendhan Temple, Vijayaasana Perumal Temple, Sri Vaikuntanatha(Kallapiran) Temple are brought on Garuda vahana.

In order to honor the processional idol of  Nammalvar is also brought on Anna Vahanam (palanquin) in a religious procession accompanied by the recitation of his pasurams  dedicated to each of these nine temples. The utsavar of Nammalvar is taken in a palanquin to each of the nine temples, An interesting thing is the idol of Nammazhwar is taken in a palanquin through  the paddy fields in the area. This festival attracts thousand of  devotees every year. The festival idols of god Vishnu from all the nine shrines will be riding Garuda Vahana, the mount of God Vishnu.  


Tirukoilur Vaithamanidhi Perumal temple  tirunelveli.toda
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The pasurams of Nammalwar and other alwars are recited as a part of daily prayers and during festive occasions in most Vishnu temples in South India.

Festivities at both Srirangam Namperumal temple and the one at  Thrukollur near Azhwar Thirunagari every year pay rich tributes to one of the most prolific poet Nammazhwar  who al last reached the heavenly abode of Vishnu -Vaikuntam. Hence the Nammazhwar Moksham (liberation) is an important, but poignant event on the last day  of Vaikunta Ekadashi at Srirangam temple. 

https://en.wikipedia.org/wiki/Vaithamanidhi_Perumal_Temple