you were right in your identification of Ash. These masses are the male flowers. Each little red blob within the mass has two pollen producing anthers. This website (if you scroll down slightly) has good close-up images of male and female flowers.
Ash generally have either male or female specimens and so will only have male and female flowers respectively. Occasionally a specimen will have both male and hermaphrodite flowers or female and hermaphrodite flowers.
This specimen obviously has male flowers, if you wished to find out if this tree also has hermaphrodite flowers you could return in late summer to see if any ash keys have set on this tree or not.