Powershell Populate ADGroup from CSV

I have populated a csv file using the following

   Get-ADGroupMember -recursive "_Escalations" | Select samAccountName | FT > c:\temp\escalations.csv

I now want to use the created csv file to populate another group

   import-csv c:\temp\escalations.csv | % {add-adgroupmember -identity _Escalations1}

And I'm getting the following message

   cmdlet Add-ADGroupMember at command pipeline position 1
   Supply values for the following parameters:
   Members[0]:

I assume this means that the csv file is not being read.

Can anyone help point out where I'm going wrong.

Thanks