{relationship_field:entry_ids} is not available in EE2, but is in EE3. Take the code from EE3 and put it into EE2.

relationship-entry_ids.diff

 .../expressionengine/libraries/relationship_parser/Parser.php  | 10 ++++++++++
 .../libraries/relationship_parser/Tree_builder.php             |  2 +-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git system/expressionengine/libraries/relationship_parser/Parser.php system/expressionengine/libraries/relationship_parser/Parser.php
index 6a7d61d21..3cb6bdeed 100644
--- system/expressionengine/libraries/relationship_parser/Parser.php
+++ system/expressionengine/libraries/relationship_parser/Parser.php
@@ -188,6 +188,16 @@ class EE_Relationship_data_parser {
 					}
 				}

+                if ($node->shortcut == 'entry_ids')
+                {
+                    $delim = (isset($node->params['delimiter'])) ? $node->params['delimiter'] : '|';
+                    return str_replace(
+                        $node->open_tag,
+                        implode($delim, $entry_ids),
+                        $tagdata
+                    );
+                }
+
 				$matches = array(array($node->open_tag, $node->open_tag));
 			}

diff --git system/expressionengine/libraries/relationship_parser/Tree_builder.php system/expressionengine/libraries/relationship_parser/Tree_builder.php
index 1fe63a25b..39a61d33b 100644
--- system/expressionengine/libraries/relationship_parser/Tree_builder.php
+++ system/expressionengine/libraries/relationship_parser/Tree_builder.php
@@ -352,7 +352,7 @@ class EE_relationship_tree_builder {
 				'tag_info'	  => array(),
 				'entry_ids'	  => array(),
 				'params'	  => $params,
-				'shortcut'	  => $is_only_relationship ? FALSE : $tag,
+				'shortcut'	  => $is_only_relationship ? FALSE : ltrim($tag, ':'),
 				'open_tag'	  => $match[0],
 				'in_grid'	  => $in_grid,
 				'in_cond' => $type == 'conditional' ? TRUE : FALSE
--
2.11.0 (Apple Git-81)